Ah, crap, sorry about that. I'm currently dumping a bunch of old keys I've had for a while, one of them being used was bound to happen eventually. Thank you Steam for not providing any way to check.

Anyways, you've won fair and square, so I've sent you a new key, it should have replaced the invalid one in your list of giveaways won. Let me know how it goes. And, again, sorry!