A guy won my giveaway and doesn't accept my friend request

Hey guys, I did a giveaway with the game "Half-Life 2", it was purchased on Steam Store ant it's limited to South America.
The problem is:
I added the winner, talked with him and sent him the game, he said that he received the game and marked as received here on SteamGifts, but I noticed that it's still on my inventory, saw his games and didn't found it there.
I tried to add him 2 more times but he keeps declining my adds. And now it's bugged and I can't add him (Error).

What should I do?

Thank you guys ;D