Jon, fortunately, did have the stone. Even if he couldn't reverse everything, at least he could tell the affected people what had happened.
"I wish that when I tell those two people what happened today, they'll believe me."
"What?" said the teenage version of his mother.
"I have a magic wishing stone, which I got from Grandpa," he explained. "After several bad wishes and partly reversed wishes, I ended up with two versions of Mom, one who is just the same as Mom, and one who is teenage. That's you two."
"Interesting," said the teenager and the woman, almost at once.
Jon continued. "I don't think I can reverse the teenager part, or do anything which changes her to anything other than a teenager. So we've got a problem. There's Mom, and there's this extra teenage Mom. You two both remember being Mom, but since the stone changes reality, other people think there's a logical explanation of who this teenage girl is."
"What can we do about it?" asked the adult Mom.
"Right now I think you have to act as if reality is real."
"I don't like that," said the teenage Mom. "Who knows who I'm supposed to be?"
"Who knows, indeed," said Jon. "Let me find out. I wish that me and both my 'Moms' here knew who the teenage Mom is in this reality."