He's not in there, he hangs around in to the left of it, next to a rock and a Drifloon. The rock is the only one of those 3 who will be there if it isn't windy.
Afterwards, you go talk to his mother in Lapis, go back to Jasper, past the Pokemon Center, but before the bridge, go down to where a policeman was being blocked off by a vine. You've got a "mini-boss" of sorts there. And go back to Lapis and that's that.