How to contact winner?

Add him, though he does have a week to mark as received i think.

Make a Support ticket.

if you wish you can always make a support ticket here on steamgifts, tho give it a week as Tomgould says after that poke support and if he dosnt respond recall the gift and ask support to reraffle =)

First, you need a banana, a steam account, a ponie and then, go and contact gaben for serious business

Okey, thank you all. I am kind of confused, first giveaway was activated almost immediately so I am bit nervous. Well, he has four days to go. I will try to add him as friend.

how do you know that he didn't activate the game if his profile is private?

today in my very first giveaway winner added me on steam , but no confirmation in SG till now :/

I can see copy of the game still in my inventory.