Is it mine or his?

if you found a ten dollar bill in the reciceling bin at the very bottom and went and told your dads girlfriends 12 year old son ,.... and he said " oohh,... umm its mine ,... i dropped it' would you belive him? cuz he lies alot and he is mean...... so now he is saying its mine.... but i say no its not...... so please answer/........... so do you belive it is his or mine cuz i found it???