Let me clarify once more, and then I let the OP and RD clear up this mess that this thread has become:
Ignore the licence, what this is essentially is bad practice from a developer studio.
A contract artist used another artist's model, received payment and probably credit for it as if it was his original work, either knowingly or unknowingly by staff artists or producers on the developer's part. If knowingly, it's even worse, if unknowingly, the OP should still be compensated fairly, especially that his work stands out from the base roster of the game.
A developer cannot just take someone else's work, justifying it by saying that the artist never had the rights in the first place, this is ludicrous. Every mod that becomes official content is (should be) paid for as agreed by the developer and the artist in advance.
Also editorial terms, such as the ones you see on Turbosquid, don't work like that, better don't say anything if you never worked in this industry before.