Showdown in Pewter City - S1-E5
Character mistake: When Brock's father takes Ash to Brock's house he tells him that Brock has ten younger brothers and sisters to take care of. But during Ash's second match against Brock you can see that Brock has nine younger brothers and sisters. You can even count them when they are all holding onto Ash to prevent him from continuing with his battle against Brock. (00:09:18)
Answer: Yes it ran away because Layla hurt its feelings.