Joe, As Bryan suggests, remove the valance board that conceals the side of the track. You will see where the door attaches to the trolley with a stud with a flat head, Pivot the white nylon retainer out if the way. lift the door just enough to slide the stud out of the slot in the trolley. If the trolley came off the door, it may have migrated down the tract out off reach deep in the pocket recess. Get a coat hanger and go fishing. Fred