At the end, when Sam is listing off all the things he has saved that "means more to him than Diane's letters", he says that he has a "double C battery".
Just before Sam pushes Diane in the chair into his office , you can clearly see the drag marks on the floor along the same path, presumably from previous takes of the scene.
When Carla returns from Graceland, at the top of the screen on the right hand side of the bar lights, the boom mic dips well into view several times.