Jon was about to put away the stone. He didn't want, after all, to keep making wishes whenever a problem kept turning up.
But he had to do one more thing... give them a way to reverse it. It had developed into a sort of prank, but he didn't want to be cruel with it and leave Joseph--who was his friend--without a penis forever.
"I wish that when a guy's penis has been turned into a girl, the girl will change back and the guy will become normal if the girl touches her feet to his crotch skin-to-skin, unless either person is pregnant."
In other words, just put her back in the same place she came off.
It should be easy for them to figure out, since it was about the most obvious way to do it. Still, Jon wondered how long it would take for them to figure it out, especially since the girl had clothes on now.
He returned to the others just in time to hear the girl named Josie.