Cannot Purge Cache

I am trying to follow a falling domino tutorial. In the attached “before” I can play the animation and the marble drops to the floor through the domino. I select the domino and click the rigid body button at the right. In the attached “After” file, note that I get an orange line in the dope sheet. When I play the animation, the ball and marble disappear after the first frame but will reappear if I scrub back to frame zero. I suspect that the orange line on the dope sheet means that there are keyframes set somewhere. But I can’t find a way to clear them. Deleting cache does nothing. If someone can tell me how, I can attach the two files.