I was just about to question if you made giveaways for games that you don't have spare copies of in your inventory - which it appears that this may be the case - the FAQ would have been the best place to start with the site - as I beleive it explains you cannot gift games that are in your own library - they are yours alone :(
sorry it appearst that you found out the hard way - I would suggest either finding a way to provide the games - purchasing keys off steam, or, if you are friends with them on steam, them purchasing and choosing to gift the copy directly to them at the point of purchase (which is allowed still) through steam - or ask for them to be deleted by submitting a ticket

otherwise - after seven days they will mark not received and you could get a suspension

this is nothing to worry about - these things happen after all :) - and it can all be sorted easily :)

so you are saying it isn't currently in your inventory? Because before you said, "I sent a gift, however, the game is still in my inventory"

If it is a new purchase, the winners need to accept your "add" if they don't accept it, it's their loss so don't feel bad for them. Take a screen shot of your add request and after 7 days, if they still haven't responded open a request new winner ticket and provide proof you tried. You could also send an email to each of the winners asking them to accept your add request on Steam.

haha, yeah ... it'd be nice if there was a "delete" option somewhere. Now that games don't get stored in inventory (except bonuses or packs) there probably wouldn't be too many mis-clicks resulting in tickets and complaints.