What utter nonsense! Do you know ANYTHING about how such processes actually worked before the Robber Church took over, strong-armed and mind-f*cked the entire formerly-Catholic world (Cooties-19, anyone?) and made a mockery of all things Roman Catholic???
Such a baptism would actually need to be supported by hard evidence. Contrary to your assertion, no one would need to prove a negative to object. All sane and reasonably informed Catholics, within Traddieland and without, vehemently object to just about every single "canonization" of the V2 "Popes" and the very process thereof. Like all they've touched, they've made a mockery of it.
There are numerous false assumptions in your comment. First, you are assuming that Traddieland is in charge of the investigation and the canonization and process, and therefore must be presented with proof of the baptism. That’s your first error. Second, you are assuming that an unbaptized baby cannot die as a martyr after baptism became obligatory, according to the general order, whereas St. Alphonsus, Doctor of the church, taught the contrary. Since your opinion vs. his is worth nothing, it wouldn’t even be a factor under consideration. Your third error is assuming that your criteria must be met for the child to be in heaven, namely, that he was previously baptized, in which case baptism would have to be proven during the canonization process.
Based on all these false assumptions, you conclude that you personally, a nobody on a forum, could object to the canonization on the basis that the child was not baptized, even though you would have know why of knowing if this criteria, which you think is necessary (actual baptism), wasn’t actually met.
What you need to realize that you aren’t the magisterium, and no conclusions you’ve reached based on your private interpretation of snippets you’ve read from magisterial docuмents matters one bit. In the grand scheme of things, what you think means nothing, and the fact that you think it does is a bit frightening.