Fish

Question

I went to an affair which was supposed to have a kosher meal for me. They didn't. Was I permitted to have a plain piece of fish? I realize that if I ordered a piece of fish that was going to be made specially for me, that I would have had to kasher the pot, but in this case the fish was already made. So do we then say that it's a bediavad case and setam kelim einam benei yomam? (