I was activating a bunch of keys from a Humble Bundle, when I accidentally tried to activate one for a game I already had. I had intended to give that key to someone else.
As I was clicking on auto-pilot, I may have clicked OK instead of Cancel. When I gave the key to the intended recipient, they said it didn't work. (Thankfully I worded it carefully, "hey, would you mind checking if this key works for you?")
Is there any way to use that key?
I have seen What happens if I activate a product key on Steam for a game I already own?, but that question focuses on getting a giftable copy of the game. That's not what has happened here, and is not what I'm looking for. I'm interested in knowing (and I'll check back with the intended recipient) if the key is still valid and usable.