The game is very common. Look around in used game stores, and you will find one, and not for over $20. (Ignore anyone stupid enough to charge over that.)

And Ebay/Amazon other online stores, though they seem to think it's more expensive all of the sudden. (Probably new AC popularity or something.

An you really shouldn't blame him if you don't have proof. Have you looked everywhere for the CD? You need to make absolutely sure before you assume those things.