That would explain why its moved, because Moses gave it a good beating
Sahih Bukhari Vol 1:5:277: The Prophet said, The (people of) Bani Israel used to take bath naked (all together) looking at each other. The Prophet Moses used to take a bath alone. They said, By Allah! Nothing prevents Moses from taking a bath with us except that he had a scrotal hernia.
So once Moses went out to take a bath and put his clothes over a stone and then that stone ran away with his clothes. Moses followed that stone saying, My clothes, O stone! My clothes, O stone! till the people of Bani Israel saw him and said, By Allah, Moses has got no defect in his body. Moses took his clothes and began to beat the stone.