Been pretty comprehensively answered above - you could quote Robert's Rules or the TDA rules or whatever you like until you're blue in the face, in a home game, house rules trump everything else and you've got to either respect the house's decision or find a new game.
Even if this had've happened in a casino though your opponent almost certainly would have been awarded the pot. Depending on the house rules in the card room he may or may not have been given a penalty for exposing his hand prematurely or trying to angle shoot (after all, he doesn't know
he's got the winning hand when he turns his card up - I'm guessing he did it to try to get a reaction out of you, and if you did something like turn your hand up and it was best he'd claim he was folding). Simply exposing his hand prematurely, and even tossing his cards near the board cards, is never going to be grounds for actually killing his hand.
If they could still be identified then I expect your cards could be resurrected from the muck, since you mucked based on faulty information, but since you had the losing hand anyway that's not going to change anything.
Originally Posted by Beanfacekilla
Yes I guess you have a point there. If he tossed them with the community cards, I guess it's not a muck.
But recently (side note), I thought one of the card rooms (I think motor city) made a rule against showing one card - even HU. I could be wrong though. I hardly ever see anyone do this.
OP should have held on to his cards for sure, until villain called or folded. Never assume....
That "can't show one card" rule is a reasonably common one - definitely in tournament play, and even in cash games in some card rooms.