[cardshark]

The guy is jumping ahead of himself. If he thought he heard her say "all-in" and he called the bet, he should have waited to see her cards first. First of all, he has the right to see her cards first (even if it is a tourney) because he is the caller. Secondly, by waiting to see her cards first he makes sure that there were no misunderstandings. A lot of players just rush and rush and then situations of this sort happen. It's not good to rush when a lot is at stake. When I call, I always insists on the aggressor showing me his (her) cards first.

So, my ruling would be that the guy was not acting responsibly. He is responsible for his own actions. If he exposes his cards, his hand is dead.

Also, even if there was no official dealer, it is the dealer's responsibility to pay attention to what is happening. From your description I can't tell who the dealer was and if he (she) was even paying any attention. This way, even if ultimately each player is responsible for his (her) own actions, at least you have a dealer (witness) who can say what exactly happened.