[Black Diamond]

Why would anyone bother to copy their 'legitimate' cdkey onto a piece of paper and then promptly 'loose' the cd case?
Obviously it is FAR easier to 'loose' a piece of paper rather than a whole cd case!
I would refer your problem to the game manufacturer and see if they will supply you a new key.
Tell them the cd key you were given and chances are they can confirm its authenticity.