I never understood why BoD was such a divisive topic among traditional Catholic clergy - to the extent of having the Feeneyites break away. There are many other dogmas that have been popular which protestants rejected throughout history. And yes, I group Feeneyites with the protestants because they can't reject any of the three types of Baptism and still call themselves Catholics. The council of Trent acknowledged the ability of baptism by desire.
If a person is seeking the Faith by all their natural and God given means, and is in a place (for example a third world country) where there are no priests, and their family is ignorant of the necessity of Baptism by water, and the person dies, can that person not make it to heaven? Are they saying that God's mercy cannot extend to the truly ignorant? Even more evident by Baptism of blood. Of course a true martyr can make it to heaven.
Now, perhaps it is a popular counter attack in response to the Lutheran: grace alone, faith alone, scripture alone. Thousands of protestants believe that the Catholic's "necessary outward signs" namely, the sacraments, are deplorable - that they should be forsaken because everyone is saved by Faith. This is easily refutable - scripture itself says that "sola scriptura" is false. The Bible does not claim to contain all that is necessary - tradition is the other pillar. From tradition, hence the sacraments, and the "works" portion - charity. Faith and works is required of every Catholic in order to get to heaven.
Now, if a person has Faith, and performs whatever works they can to seek out Baptism/ entrance into God's church, but does not receive the sacramental baptism through no fault of their own, they could make it to heaven. They are still not counted as members of the church, but their soul may be saved. I say "could" because we cannot ever say for sure that someone is damned. The exception would be those few in history whom God has revealed are in hell. Judas, for example. By action and desire, a person may deserve and receive grace from God enough to save them. Remember the suicide jumper who made it to purgatory because from the time he jumped until before he hit the water he asked God for forgiveness with a sincere contrition. Another example: the good thief... "this day thou shalt be with Me in paradise".