Out in the hallway, Jon wondered why Mikey told him to leave. Yes, Mikey had Zoe's personality now, and Zoe always kicked Jon out in the rare occasion that he visited her. But Jon was still curious about it.
He took the stone out of his pocket and said "I wish that for the next 20 minutes I would be in Mikey's room and that during that time, Mikey will not notice my presence."
The stone glowed and Jon disappeared from the hall and reappeared inside Mikey's room.