Okay. Then Where The Heck Is Emmet And When Is It His Turn? - Tumblr Posts

Not at all where I thought it was going, but get this: the displacement was Arceus's direct response to being banned from the Battle Subway, but not out of spite. It was just trying to follow the rules. "I'm not allowed to battle you here? Okay. We'll battle there."

That's the condition for going home: Ingo just has to battle Arceus. The outcome doesn't even matter.