What happens if we're heads up and the board is AKJ83 and I have Q4, my opponent has 99. I am dealer, he was small blind. We both check and I say "Oh my God I have a monster". He then folds before either of us show cards. I turn mine over, showing the bluff. Who wins the pot? Is he able to say well, oh I have 9s or do I win?
It is a players responsibility to table and show their hand and most importantly to not muck their hand. By the sounds of things the player has mucked his cards, those cards are now irretrievable, you win as you have showed a hand which cannot be beaten on account of you being the only one with cards left.
Anyone could say they have anything. It's up to the player to protect and show and prove their hands to win the pot. You cannot retrieve the hand in this instance.
However, what you did is an absolute angle shoot, be careful with this, you don't want to develop a reputation for this. People don't appreciate it, you set yourself up for round penalties in casinos and card clubs, and perhaps even more depending on the severity of it.