meaby he is sending a Key to the winner
If not, use the Support

Wait a week, then mark as not received. If you still didn't get it, ofc.

Well you can't do anything except of waiting for a week, and marking the gift as not received.

After a week, mark it as not received and report him.
A guy who was supposed to give me a steamcode hasn't done so in two weeks even though his last online was 5 days ago. It would be surely easier if we could contact other users without having to add them as friends on steam...

check your e-mail

Check you email, if there's nothing there wait a few days.

If the giver didn't contact you within 7 days you can try to add him again but some people actually find it rude when people pester them about a giveaway and will wait for the last minute to give the game away when someone does that. (I personally find it childish but hey, it's their game to give.)

If you haven't received it after 7 days, and you still can't contact the giver, then mark it as unreceived and move on.

If the giveaway is the one I'm looking at, and the reclusive "gifter" keeps declining your friend requests, I wouldn't hold your breath...

wait for a week and still nothing marked not received.

guess it is one of these special cod giveaways :(

Yeah just wait the seven days and mark it.
I won Sniper Elite V2 five days ago and it was fake too, it sucks. The green bar keeps taunting me