Yep, it is confirmed that it can, and does happen. If you remove an animal but it's still in your trade center your visitors can still get the desire to see it. To solve it you need to move the animal to a different zoo. You can move it back to the trade center from that other zoo if you want, at that point it will be associated with the other zoo rather than your main one.Someone wanted to see a Grizzly in my Zoo but I have no Grizzly in the Zoo. I had Grizzlys in the Past. Maybe this can happen if a Animal is in the Trade Center and still assigned to the Zoo