Mikey was confused. Not only was he unexpectedly in his mother's body, but his original body was acting as if nothing was wrong. He found himself mumbling "I wish I knew what happened."
Then Mikey did know.
When Mikey wished for Jon to do what he says, the stone simply fulfilled the wish in what would to it be the simplest manner. switching minds/souls was merely an exchange of energy, with the twist being that only the mind that made the wish retained all the knowledge of his life, especially with respect to the rock, and the other mind, his mother's, only remembering Mikey's life but without knowledge of the rock. For all intents and purposes she thought she was Mikey.
Mikey calmed down a little. Jon, Karyn and Mom/Mikey were all giving him/her a weird look. "Uh, no I thought I lost something in here earlier. "catch ya later guys, 'kay!?" And with that Mikey headed back downstairs. Maybe this'll be fun for a while. I can play games an' eat all I want....maybe even have Mom go to school insteada me.