From the article:
"He is such a dynamic and exciting character," Clone Wars supervising director Dave Filoni told USA Today. "He made such a huge impression in that first film that when you go back and look at the prequels, you forget he's not in all three."
PAH! Don't make me laugh, he had about 3 lines in the entire film and just stood around grimacing. People only remember him because he had a double bladed lightsaber and cool face paint.
He was stabbed in the gut and cut in two, then fell down a several hundred metres long tunnel and forgotten about. How the blazes could he have survived that? That's a pretty blatant and completely terrible Deus Ex Machina, but aparently it was all Georgeyboy Lucas' idea, so I shouldn't be surprised.