Ghost Snapshots: Vader Ghost?

Jose from Dallas, Texas sent us this fun snapshot of Halloween costumes (in this case the Dark Lord, Darth Vader) and a shadow that appears on top of both pictures. Shadow ghosts can appear like this, but we are wondering if a stray finger got over the top of the camera's flash unit just a bit. Is it a ghost?

"...just posing for pics before a Halloween costume party..."