I have a question

Civ V uses steamworks, so if you have a physical copy you had to activate it on Steam in order to install and play it.

U sure you didn't activated your key? As far as I know there's no way to know which key was used for it D:
You could also try activating your key, if it works you'll get "You already have this game" if it doesn't it should say "It's a duplicated key" might work as you already got the game, not 100% sure if you'll get the duped key message if it doesn't work but it's worth the try :P

PD. SOME games tell you which is your key but that's when you need it for another kind of in-game registration like games for windows

You played 11 hours of it, and you're surprised that it's in your library?

Perhaps a bonus with another game you activated? It has been a pre order bonus before IIRC.

Did you just get the free copy of Civ from voting in the golden joystick awards like many others have?

You better edit that mail on the first pic.

i would edit and the account name too.

You won it on SG: http://www.steamgifts.com/user/SilenR/won
??