Key activated different game than stated in giveaway.

Message the giveaway creator and let them know the key was for a different game. It could have been a completely honest mistake that they will be able to rectify. If they are unable to replace the key with a working one then you can agree to have the giveaway deleted.

If they try to persuade you to accept the different game and mark it as received do not do so, mark as not received and move on.

As you already talked to the giveaway's creator, just wait 7 days and mark it not received then.

Ask the GA creator to create an invite only GA just for you, for that game you won, and after that accept to delete the other GA.
I think this is the best solution for the creator and yourself.

If you win Glowing Sokoban you click received after you receive that game. You can let the giveaway creator know the key was wrong and ask for a new Glowing Sokoban key, and if they don't give you one within 7 days mark it as not received. Or you can allow them to delete the giveaway if you feel like being nice.

Also, double check whichever game is actually in your library. Occasionally, Steam will report the wrong game activated, but that's usually also after trying to activate a key for the wrong game too (something like that... memory is hazy on the details).

Thank you all for helping me. I went with @sa4zet solution and it worked perfectly :)