Why is it a travel?
AFAIK, a travelling violation requires player control of the ball, which is lost when a player fumbles. The reason why the ordinary "up and down", i.e. jumping in possession of the ball and landing with the ball, is a travel is that a player removes and replaces his pivot foot without releasing the ball. He controls the ball, yet tries to cheat the restrictions on moving the pivot foot = TRAVEL.
A player who fumbles the ball
accidentally loses control of the ball, does not look to gain an advantage (rather he puts himself at a
disadvantage), and has released the ball, although unintentionally. Once the ball has left his hands, he has no control of the ball, and no pivot foot. Therefore, it makes no sense why a player who fumbles the ball on an attempted try should be punished with a travel, in the same way that the NBA rule penalizing a player who shoots an airball and catching his own rebound with a travel also makes no sense.