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The Sacrament St. Thomas was referring to is the Eucharist, not baptism.

What did he teach that was controversial about the Eucharist that did not also apply to a BOD?  He admitted he could be wrong, no such admission is offered by the Church pertaining to defined dogmas.

Why insist on posting the contradictory-to-dogma opinions of the lesser authority of St. Thomas and other great saints?

Do you believe them to have authority over defined dogma?
 

St. Ambrose: “But I hear that you grieve because he did not receive the sacrament of baptism. Tell me: What else is in your power other than the desire, the request? But he even had this desire for a long time, that, when he should come into Italy, he would be initiated, and recently he signified a desire to be baptized by me, and for this reason above all others he thought that I ought to be summoned. Has he not, then, the grace which he desired; has he not the grace which he requested? And because he asked, he received, and therefore is it said: 'By whatsover death the just man shall be overtaken, his soul shall be at rest.’ (Wisdom 4:7).”

As addressed, oh, about 50 times now, this is totally ambiguous.  But let's go through it again.

This could just as easily be a reference to a Baptism of Blood, since Valentinian was murdered precisely because he had rejected Arianism.

Also, it could reflect a possible hope that someone near Valentinian baptized him as he lay dying.  Back before the days of the internet, the details were probably sketchy in terms of what actually transpired.

Finally, it could just be a generic statement that he received what he sought, implying that if he didn't receive it, it was because he didn't REALLY seek it.

Elsewhere, St. Ambrose rejected the notion of the possibility of salvation for even virtuous Catechumens if they do not receive the Sacrament.

Finally, when St. Augustine was speculating about BoD, he cited no authorities, other than St. Cyprian's belief in BoB ... and then extended it.  If St. Ambrose had believed in it, surely Augustine would have cited it.

In terms of Baptism of Blood, there's evidence that the (handful of) Fathers who believed in it considered it to actually be the Sacrament of Baptism administered in an alternate mode, with the blood being the matter, and the angels pronouncing the words.  St. Cyprian called BoB a Sacrament.  There's an ecclesiastical manual that for the longest time had been attributed to St. Augustine, and was certainly written by someone in his circle, which says that the only alternative to the Sacrament is in fact BoB, since "all the sacred elements" (aka matter and form) were present.  St. Cyprian described martyrdom as having the martyr washed in his own blood while the angels pronounced the words.