O.O This.... never occurred to me. Fuck.
Alot of adoptees should think about this.....

I just reviewed some basic copy write law regarding freelance art work, and unless it was expressly stated in a contract and signed by both parties that the copy write of said adoptable character was transferred to you, then the artist is in their rights to do this. (as bad as that is). and you are also not allowed to have any other artist make additional works of said copy written characters without the original artists express permission. (this is why the copy write of the works should be transferred to the buyer when selling an adoptable).

I would contact the seller and get an agreement in writing for the copy write of the works and characters mentioned. If they refuse to be provided, demand a refund. You -can- actually sue the artist for the copy write of the works if you wish. Especially if the language of the transaction indicated that you would have all rights to the character and works after the transaction. No guarantee that you would win without a contract and written agreement of the copyright transfer signed by both parties, but you might have a strong case.