Get something to sit on and sit in front of the tank and watch for a while. Be still and patient. you should see him or her come all the way out of the hole once or twice, and get a good ID.
If the shrimp is small, then I would suggest leaving it alone. I doubt that the pistol shrimp can damage the glass of the tank, nor would it be harming th eother inhabitants of your tank, except for hermits that are stupid and venture into the tunnels the shrimp has made.
As for the snapping sound it makes, well... My tanks are next to my bed, and I have no problem sleeping with the pistol snapping all night long. Mine's also pretty small still.
One reason mine snaps all night long is the bristle worms invading my tank, and the shrimp's dwelling.