Sorry to hear about your poor fish.
If it were me, I would definately post him in the vendor's forum and explain what happened. Why? Because no matter what, any business should honor thier fish, or any product for that matter. He should have atleast given you a credit for another one. Also, if any vendor acted like this, then I would want to know before purchasing from him. It's pre-informing other potential-customers what they could be getting into.