No, it is not a flyball out. The rules specifically state that a player may not try to stop the ball by throwing a glover or mitt, a belt, cap or other paraphernalia to stop a ball. The important thing is that he had the ball for the out.
Here’s another classic. Carlos Martinez (Indians) homers off Jose Canseco’s head.
http://www.youtube.com/watch?v=S9StStOsFpg