I apologise for Being Away.

Well, I have to add that your post did not contain text at the time I wrote my first reply :P

Anyway, to answer your question: You have to try to contact the winner by mail, even if he does not accept your friend request.

If he does not respond within 7 days after the giveaway ended, you take a screenshot of the mail and request a new winner (link the screenshot in your ticket to get a re-roll approve faster).

Since the GA ended 1 day ago, I'd say send the mail now and wait 6 days - nothing you can do in the meantime but wait =)