Plot hole: When the Chicago Post first runs the story on Kevin, there is a picture of him on the front page, next to the headline. So anyone who was following the story would have known what he looked like, which would make it impossible for Kevin's friends to get away with pretending to be him.
Plot hole: Kevin is waiting at the train station for "the L-girl", and she sends a paper plane down to Kevin to get his attention. By this time the reporters have lost interest, and are turning away. Kevin looks up and starts to walk towards Abby, and the TV cameras start to run up to Abby to get a shot of her. Only problem is, How did they know what she looked like? Kevin is the only one who knows that she is the "real" L-girl.