Thanks for playing and for the bug report! I have a good lead on why the eel may have disappeared but the circumstances are too rare for it to be considered a "game breaking" bug, so I don't think I'm allowed to fix it for now unfortunately
As for Yorick, its recipe is any crafting attempt with 3 or more of the base ingredient (bottled purple ingredient) but without fulfilling the recipe for any of the other existing takodachis. Essentially just meant to be the result of messing up a recipe :)