Problem with a bundle key (giveaway)

Hello everyone! Let's see if you can help me with this. I know it's a bit annoying.

Last Christmas I won a key for a bundle in the official steam forum. The problem is... I never knew what bundle is the key for!! I was going to add the key to my steam account when it said that I already have those games in my library.

I tried to contact the one who gave me the key, but he never replied.

So, I have a key that I'll never use but I don't know what's it for. I only have two bundles:

Humble Bundle #3: Crayon Physics Deluxe, Cogs, VVVVVV, Hammerfight, And Yet It Moves.
Frozenbyte bundle: Trine, Shadowgrounds, Shadowgrounds Survivor, a pre-order for Splot and a prototype Jack Claw.

Obviously, the key is for one of those bundles, but I can't know which one...

When I add the key to steam, there's no problem with that, only the "you already have those games". I'm pretty sure that the key is working.

I want to giveaway the key on steamgifts. How could I do that?

Thanks for the help and sorry for my english!