Counterfeit bill

Today I went to exchange some US dollars for euros. Turns out that one 50USD was a counterfeit! Excitingly enough, the woman gave me a suspicious glance as I widened my eyes in pure innocence and confusion. (Small Asian Girl no try to cheat noone) Actually I would like to have my bill back so that maybe I can use it on a fake Gucci. Of course I didn't get it back, although she did give me a photocopy of it.