I agree with you that most cases of thumbless-grip bar slips do end up on the lifter's chest. (Lots of YouTube evidence to this effect.) However, I have seen videos wherein the bar ended up falling on the lifter's throat, presumably because the bar-path was up and headward.
That said, I don't know for a fact that he was using a suicide grip; it was an assumption on my part. Have you ever seen or heard of someone losing the bar on the finger-side? (I haven't.)