B737 flight Attendant reports discovering a man in the emergency exit row during beverage service wearing a mechanical prosthesis in place of his right arm and asks him to change seats. The passenger refuses. A specific statement about passengers wearing a prosthesis in the emergency exit row cannot be found in the Flight Attendant Manual.

Narrative

Approached a passenger; in aisle seat in exit row; at beverage service because he had a mechanical prosthesis on his right arm encompassing most of his arm and his hand. I asked him to change seats; and he became agitated and demanded proof. I searched manual cover to cover and was unable to find anything that said prosthesis not allowed. Contacted Captain; to let him know what was occurring. He advised to allow passenger to remain in exit row. At recurrent in May; I personally asked a question regarding exit row and passengers with prosthesis. I was told at no time do they meet the criteria. Passenger feels harassed; I feel stupid because I have nothing to back up my claim. Please put an detailed narrative in the manual regarding the exit row criteria that is not vague. Very hard to back facts up if they don't use words like prosthesis. Or; if I am wrong; please advise trainers of proper training as I specifically asked a question regarding events such as this recently and was told no one with a prosthesis is eligible.