they believed that Scripture was silent on the topic

The literal sense of Scripture (as opposed to allegorical, etc.) is the meaning that God intends for us to understand about what is actually occurring or described.  This does not mean that God intends for us to take figures of speech or parables as literal descrptions.  The Church guides us in understanding the meaning that God intends for Scripture.  Only sola Scriptura heretics take everything in Scripture literally.  (And yet they somehow miss that "This is my Body" is literal.)

We can best understand St. Augustine's view how it is used in magisterial teaching, here in Providentissimus Deus:

To understand how just is the rule here formulated we must remember, first, that the sacred writers, or to speak more accurately, the Holy Ghost "Who spoke by them, did not intend to teach men these things (that is to say, the essential nature of the things of the visible universe), things in no way profitable unto salvation."(53) Hence they did not seek to penetrate the secrets of nature, but rather described and dealt with things in more or less figurative language, or in terms which were commonly used at the time, and which in many instances are in daily use at this day, even by the most eminent men of science. Ordinary speech primarily and properly describes what comes under the senses; and somewhat in the same way the sacred writers-as the Angelic Doctor also reminds us - `went by what sensibly appeared,"(54) or put down what God, speaking to men, signified, in the way men could understand and were accustomed to.

I have bolded the Augustine quote. (And Ladislaus, please stop the nonsense claiming that quoting this encyclical somehow puts me on a "trajectory to modernism" merely because modernists have misinterpretted it according to their agenda.  What haven't they misinterpretted? This is their basic mode of operation.) 

So here we have clear magisterial teaching that the intent of God in Scripture, therefore its literal sense, is NOT to describe the physical nature of the visible universe.  When it speaks of such things it is using figurative language.  To claim that Scipture teaches the earth is flat is to go against Church teaching on how to understand Scripture.

Ordinary speech primarily and properly describes what comes under the senses; and somewhat in the same way the sacred writers-as the Angelic Doctor also reminds us - `went by what sensibly appeared,"(54) or put down what God, speaking to men, signified, in the way men could understand and were accustomed to.

Leo reminds us the sacred writers weren't seeking to penetrate the secrets of nature, however, that certainly doesn't mean the earth is inscrutable, or Scripture was false or wrote the opposite of what it meant. Rather, the writers went by what sensibly appeared, and in a way men could understand and were accustomed to, as Leo tells us.

This is why the Fathers of the Church wrote exegeses from Scripture comparing the earth to the tabernacle, with a domed ceiling like a tent, pillars, walls, and a division between the holy of holies and the outer part where men gathered.  The model for the tabernacle (as well as church architecture) is all of creation, with heaven and earth divided by the firmament, separating the holy place of heaven from the men on earth, where God is worshipped, yet apart from where he resides.  This is why the Fathers described the earth as a two story house.  Simple enough language that cannot be reconciled with earth being a ball.

If this is unfamiliar to you, it's only because it has been hidden from you by the enemy, or forgotten, or both, which is the way the enemies of God operate throughout the centuries. God's enemies literally buried the true cross which remained lost for centuries.  This kind of thing happens, but we ought not be resistant to what Scripture says, especially when the Fathers expound on it. We should happily abandon the pagan indoctrination we suffered, being so contrary to Scripture and the Fathers.. 

Your interpretation of what Leo says suggests creation ought to remain obscure or inscrutable, both philosophically and physically.  Or maybe that only scientists have the answers.  I'm not denying such things aren't incredibly deep and spiritual, just that God intends for us to contemplate things so He can reveal more to us. God tells us to knock, seek and ask.  I haven't seen globe promoters attempt to consider the mysteries presented, let alone to find alignment with the Fathers, Scripture and reason.  Instead, some prefer to obscure understanding telling everyone not to bother, there's nothing to see, leave it to the scientists. Even when you catch them lying, I guess. Let's be honest, they tell some whoppers: When Scripture says the earth never moves, the lying enemy says it moves 4 different directions at high speeds.  When Scripture says the sun moves, they say the earth does.  When Scripture says stars are lights, they say stars are worlds, even with alien beings. When Scripture describes water above the firmament, they say it's empty space.
 

  How much have you read about Galileo?

...I'm still waiting for you to correct/accept that St Augustine confirmed that God (literally) spoke: "Let there be light".

Your interpretation of what Leo says suggests creation ought to remain obscure or inscrutable, both philosophically and physically.  Or maybe that only scientists have the answers.  I'm not denying such things aren't incredibly deep and spiritual, just that God intends for us to contemplate things so He can reveal more to us. God tells us to knock, seek and ask.  I haven't seen globe promoters attempt to consider the mysteries presented, let alone to find alignment with the Fathers, Scripture and reason.  Instead, some prefer to obscure understanding telling everyone not to bother, there's nothing to see, leave it to the scientists. Even when you catch them lying, I guess. Let's be honest, they tell some whoppers: When Scripture says the earth never moves, the lying enemy says it moves 4 different directions at high speeds.  When Scripture says the sun moves, they say the earth does.  When Scripture says stars are lights, they say stars are worlds, even with alien beings. When Scripture describes water above the firmament, they say it's empty space.
 

Jaynek:  In the Middle Ages, educated Catholics ... believed that Scripture was silent on the topic and that it was a matter for science.

Ladislaus:  It's the same thing with Sacred Scripture, where there's no unequivocal statement about the earth being flat, just some passages that may imply it.

Jaynek:  Thank you so much for explicitly saying this.  I have noticed that you typically support your belief in flat earth with arguments from science.

Well said. Your entire post explains the subject very well, but the above shows the problem, IMO, with the globe-earthers wanting to keep science separate from religion, as if God isn't the author and creator of everything in the natural world.

To say that something is implied is also not being silent on the matter.

Some of the greatest dogmas of the Faith are only implied in Scripture.  Tradition fills in the gaps.

But there is no Tradition that the earth is flat or that Scripture teaches it to be so. Catholics throughout history, including Doctors of the Church, believed, as a matter of science, that the earth is a globe. 

A globe in the sense that was taught by Aristotle and Ptolemy, not a flat earth surrounded by a globe-shaped firmament.

And these Catholics could only accept this scientific model because they believed that it was not in conflict with Scripture.

How could St. Thomas have taught that Aristotle's understanding that the earth is a globe is correct, if there was an existing Catholic tradition that Scripture taught it to be flat?   And it was not just St. Thomas, but every educated Catholic, at least from time of St. Bede on, who believed that they were free to accept the view of pagan science on this.