Question about Raymer's hand

[Matt Williams]

I'm pretty sure I know the answer to this, but I want to double check here. There was a hand where Raymer didn't hear whether the guy called or went all in. Raymer said he heard the "all" part but wasn't sure if "call" or "all-in" was said.
Let's assume he thought the opponent said "all-in". Raymer then says "I call" and flips over his 2 cards. Would his hand be dead automatically for showing his cards to a live player?
I know a player like Raymer wouldn't act so fast and show his cards before the other guy, but let's say it happened to an inexperienced player.