Report a user?

Post a support ticket.

Edit: and it's likely the user won the game twice but one of those giveaways could of been fake.

Just make sure the first time they won they actually received it. Just click on the first giveaway, just underneath the banner for the game it will show the winner, and beneath that it will either say they have received or they haven't received the gift.

A hint...take a look at the guy on latest recived who won hacker evolution untold