Oh, man... The winner has to mark as not received now, as all won games have to be activated on the winner's account, otherwise they risk suspension and will be barred from SGTools protected giveaways. Plus you'll probably land a short suspension for making a misleading giveaway, putting that disclaimer in the description doesn't guard against that.

For future reference, if it's not in the list, it's not allowed to make CV-giving giveaways for it, as it's been given away in mass quantities in the past. If you still want to give away such keys anyway, you can use KeyGiveaway or make an event in the forum where, say, you ask people who had it wishlisted before the event to post a comment, and you manually draw a random winner among them after you get enough entries.