You had a good idea, gift cards sell well on Listia, but you shouldn't ever show the card's code. There are lots of dishonest people around who will gladly steal your money.
Personally, if what the others say is true, and the money is gone, I'd see if you could lodge a complaint with Apple, find out who used it, and call the police.
Hopefully the thief was stupid enough to use his real info when using it.