You just have to read all of the journal pages on the shelves, check every corner of the shelves, all of the Poke Balls, and the punk guy will tell you something like "Nothing, eh? Well I'm leaving for the day, shut off the lights when you leave." If that doesn't work then the game might be glitched or something, it might not be a bad idea to save and soft reset.
Source: Experience through the full game of Y
