Continuity mistake: When Ash, Misty, and Brock are talking while they follow Pikachu, the button on Misty's shorts goes from blue to yellow constantly. (00:02:29)
Other mistake: When the camera pans across the Pikachu when they are surprised, one of them is missing its cheek pouches while another is missing its left one. (00:03:06)
Continuity mistake: When Brock says, "Yeah, I don't think too many people come this far into the forest, Ash," there is a tree with three branches directly emerging from its trunk, but in the next shot, it has two. (00:05:03)
Revealing mistake: When Ash goes to save the Pikachu in the river, he clips through his and Misty's bags. (00:05:25)
Answer: Yes it ran away because Layla hurt its feelings.