"I wish that I would never enter the green stone ever again," Jon said. He smiled, thinking that he had beaten the stone at its own game. But then he felt that familiar feeling of being pulled towards the stone. "Wait! I wished that ..." Then he was suddenly surrounded by darkness. He was inside the stone again. Why didn't his wish work?
Thomas looked down at the green stone in his hand. He was out! What a relief! Any longer stuck in that dark place and he would have lost his sanity. He didn't like darkness.
But what about the boy? From what Thomas figured, when someone made a wish, they switched places with whoever was in the stone. But given Thomas' nyctophobia (fear of the dark), he didn't think he could make another wish. He didn't want to go back there. He didn't care if that boy was stuck there. As long as it wasn't him.
But maybe he could give the stone to someone else and they could make a wish and switch with the boy. But who?
What Thomas didn't realize was that Jon's wish (to never enter the stone again) was granted to him. That's the way the green stone worked. Someone makes a wish, then the wish is granted to whoever is switched with the person in the stone. In this case, Thomas.
Even if he did make another wish, Jon's wish would prevent him from entering the stone again. But, of course, he didn't know this.
