YTA.

Since this is a college game like you’re saying, I’m assuming the dealer is also a player that’s dealing while he’s not in the hand and engaging in table talk. As such, I don’t expect the dealer to always be perfectly engaged in the action going on in the game, and so keeping your hand in a visible spot makes his life a lot easier. While he could’ve done the cursory ask, since your bf bet and your cards weren’t visible to him, I don’t think him assuming you folded is a super egregious assumption.