I was working the dish in an American Legion U19 game Saturday evening. In the third inning, the visiting manager informed me that the home team had two #13 on their lineup card. This surprised me since I normally do a thorough scan of both lineups at the coaches meeting, but this one got by me. I notified the home manager of the error and requested that he remove the wrong #13 (who was wearing #17) from the game. He, to my surprise, co-operated and sent in a sub. He blamed the error on the assistant coach who filled out the lineup. I scowered the rule book and all my manuals with no luck. I found the rule that if an obvious error in the lineup is noticed by the umpire before he signals "play", the error is to be corrected with no penalty. But what is the penalty if the game has already started?? After the game my partner working third thought I should've just corrected the error when it was noticed and my partner at first didn't know. What do you guys think??? Is there an approved ruling??