i want to know who really used my iTunes code.

I buyed an iTunes code (100 euros) via 'cardscodes.com' reseller for a gift to a friend. I sent the code to the friend for recharging a game for his kid, but he said to me that the code was already been used !

This was impossible on my side then I suspect a scam.

Ther question is: Is it possible trace back to the real user of the code ? or at least if the code has really been used by someone after my procurement of it ?

Take into account that just few minutes ago I tried to redeem my code but the system says that the code has already been used.