During the film, there is a moment when Daniel Craig's character rides away from the town to find his old cabin in the desert where he last saw the woman he loved. As he is riding up to the cabin, the film shows a wide shot of him with his left hand holding the horse's reins to guide it up a small rise. As the alien weapon/device is supposed to be on his left wrist, it should still be on there during this shot.

However, in the wide angle shot his left wrist is bare as he holds the reins and it is obvious that the device is nowhere to be seen.

In the following shot it has returned to the proper place on his wrist.