Batter out for throwing bat

[jodibuck]

In our local NFHS clinic, our clinician was discussing a "war story" about calling a batter out for throwing her bat. After a little questioning, it appears she had warned the batter earlier in the game about tossing her bat after a base hit. Apparently, this player did not approve of the umpire's warning. After her next base hit, she tossed the bat in the direction of the umpire's head. When the play was over, the umpire called the batter-runner out and restricted her to the bench. In this situation, the thrown bat did not interfere with the defensive team. Where in the rule book does it declare a batter out for tossing the bat?