Oh Mine did that! He loved his "big boy bed" when he was 2 - played on it, napped on it, but sometime during the night he would get up and dragging his blanket with him, and wind up on the floor of his room. One morning I found him sleeping on the floor in the hallway between our rooms! What he was really doing was half waking up in the middle of the night and coming to sleep in my room. But, since he was never fully awake - he just collapsed on the way and went right back to sleep wherever he landed.
After I found him in the hallway and because we had hard wood floors (he already had a nice rug in his room) I started to put large cushions next to hid bed. This kept him from getting very far from bed and when he fell back asleep at least it was more comfy for him.
He finally just outgrew it.
You may want to try leaving his bedroom door open and putting up a "baby" gate (as long he doesn't climb them). That way in the morning you could easily just pick him up and move him. Try putting the bed against the wall and creating a pillow "barricade". He will outgrow it. Mine is now 14 and doesn't sleep on the floor anymore! LOL
Sleep tight....