When you understand these two points ... you understand why the laser beam comes back to earth

(1) I am sure you are aware that the moon does rotate. (Its rotation happens to be 27.32 days, and its orbit around Earth is 27 days)
and that
(2) We, from Earth, see the same side of the moon all the time.

"Sychronous Rotation" is one of the things that makes our moon so special. The moon's rate of rotation nearly matches its orbital period. This amazing fact means as it rotates around Earth, it too is rotating just fast enough to keep its "Face" facing earth. You might have heard of the Dark side of the Moon and that we never see it. Well its true we have never seen the Dark side of the Moon from Earth, the First Time was the Apollo Missions and their pictures they recorded.

http://www.space.com/24871-does-the-moon-rotate.html
http://discovermagazine.com/2014/dec/2-ask-discover
https://www.universetoday.com/19699/does-the-moon-rotate/

This is why a laser beam shot at the moon comes straight back because the moon is always facing us.
or Google it ... nice try though