While I also had noticed that the little fish figurine up for auction was actually "Flounder", and not (as far as we know) a friend of "Nemo"- I do not find the "error" to be one so serious that speaking rudely to the seller becomes necessary, or acceptable...
** "The Little Mermaid", and "Finding Nemo" are both fictitious stories. Fish do not talk. There are no half-human mermaid princesses. Princess Ariel does not exist. If she did, the only "fish-friends" she would have would be the ones that found her to be "fish-food", after she sucked water into her lungs, and sank to the bottom of the sea. Fish do not talk... These are stories we made up for fun. For the imagination. All boundaries are lifted. No rules apply... And with that- who is anyone to say whether "Flounder" was or was not a "friend of Nemo"? It's all made up anyways. Cannot be dictated as fact!! I think it is quite possible they may have crossed paths- down there "under the sea"!!!!