Hmmm...I would think the persist behavior would have a 'clear data' action, but it doesn't. 'Reset All'...that would be an interesting addition. Two work arounds:
Lame idea: Browser -- Reset Page. Not the most elegant solution, but...
Good Idea: Save states: Just save the initial state of your game when it starts, and restore it after game over. That should reset everything. Course, it might lag a little if your game has lots of objects and data.