Player on the floor

[LepTalBldgs]

Saw a game today and had this question.

If there is rebounding action and the offensive player falls to the floor trying to get a rebound but a defensive player grabs the rebound, what do you have if the ball handler trips over the player lying on the floor and loses the ball? Is your answer different if the player is just lying there versus actively trying to get up?

Sorry if this has been discussed before but I don't remember this being addressed in the case books.