if i remember right the moon split in two one half went behind a mountain (i think) and the other went to another side
It was a miracle for the people of Quraish and they still didnt belive
the moon went back together after that

BTW i read somewhere that some astronauts have found a crack on the moon that goes all around it. (which prooves that the moon had split in half before)

i'll try to find more info inshallah