Bubbles had still been following the group. He may have totally failed back there, but he was still kind of lonely. Climbing up trees all day would bore anyone. He had noticed that the group went inside a Pokemon center. "Shoot, now I've lost them..." He looked around, before laying down on the tree branch he was on. He tossed a small ball of Frubbles up and down, thinking.
Bubbles continued to think, How do I get to them, and how do I make them think I'm not a clumsy idiot? He watched the Pokemon Center for when they came out. All that waiting was more boring than just climbing up trees, and he managed to fall asleep. And then he fell off the tree and landed on his head, which as you can expect, knocked him out.