You should add him and wait for a week or so....may be he could be back in a day or two?

You mean they weren't online immediately to receive your gift?

OHTHAHUMANITYYYYYYY

Last connection steam: 19 days
in steamgift: 1 hour

He has 7 days to receive the game and to mark it as received.
I doubt you can get back a gift you sent by email though, but am not sure.

I don't know if you can cancel the gifting process, but you should definitely give a guy some time (I mean days, not hours). When he notices he has won something here, he will probably log in to his steam.

Check the rules - he/she's got seven days to get in touch and receive the gift. No need to worry just yet!

I'm not sure if I understand this correctly...

your giveaway had timelimit set for 2 hours -> that means he was active/alive 2 hours ago

On steam it show you that he was active 19 days ago because he might have set on his profile "Offline" mode. Don't worry he is probably still alive...

You may ask for re-roll after 7 days (if he won't show up)

You do not need to send him/her the gift/key immediately, you can simply try to get in touch first, either by adding him/her on Steam or sending him/her an email.

If you can't get in touch with the winner within 7 days, create a support ticket (or a re-roll request) and add proof that you've failed to contact the winner both on Steam and by mail.

If you've created a support ticket, a mod will most likely tell you to create a re-roll request.
If you've created a re-roll request, a mod will grant the request when he has time - as long as you've sent in some proof that you could not contact the winner.

I already send the gift :/

the support sucks anyways i had one winner and since a week after the giveaway i wanted new one the staff said they wanted a proof so i gave them and i had to wait anoter 3 week till that person decided go accept the gift