Oh, I know who you are talking about. George got rid of him because he thought that people would get confused with his species and the Kaminoians. He got rid of Yaddle because he already had a digital Yoda and he did not make another CGI Jedi. But the true story is that they died between Episode I and II, Yaddle dies from a nuclear explosion, and(like you said) Yarael gets killed by a mobster.