What do I do? (got code for wrong game)

I won this giveaway : http://www.steamgifts.com/giveaway/wCfcj/siege-of-turtle-enclave for the game Siege of Turtle Enclave, but got a code for the game Enclave itself, which was given away not so long ago for free. so what do I do from here? just mark it as not received? I added the maker of the giveaway but he went offline and doesn't seem to understand me. advice please! :)