Deleted

It should be on your library. Restart Steam.

If you accept once, then it will be forever in your library.

You deleted the email, look in your 'deleted' or 'trash' and after putting the code in it should be in your library.

I just lost The Game...

check your inventory

fail

Get a gmail account.

I see it was portal. go here

It should say you already have game in place of price (assuming your logged in)

well, your game library does not show that you have portal since that is what you won, so according to steam you have not claimed the gift which means the person that gifted it to you should still have it in their inventory and can resend the gift. So I guess all you can do is wait for the gifter to resend it, but if it is gone from their inventory as well then you and the gifter will have to contact steam and let them know who sent the gift and that you clicked the link for it but it is not in your library.