I gave away a game 2 years ago, and I'm not considered a contributor?

It's marked as not received.

Edit: Maybe you gave him a copy of Sanctum while the ga was for Sanctum2?

Have you noticed it not marked as received anymore? You should try to contact the winner.

If that doesn't work out contact sg support

Did you actually send the winner the game?

If you did, contact SG support to get things sorted.

The giveaway is marked as Not Received, so that means you didn't send the game, or for some reason he didn't receive it or didn't work or something like that. If you did send it maybe contact the winner to see what happened.

Winner have to mark it as received.
In case if you didn't know, you have to click "Send Key" to make the key appears on winner account

*edit: Probably you give a key for "Sanctum", not "Sanctum 2"

You can make another giv. But that guy hasn't logged in in like 4 months, so contacting them might not work.
If he owns the game, support might be able to "fix" it for you.