"I wish I knew how this was happening," Jon said. His wish was granted, but not to him. Instead it was granted to Zoe.
Suddenly, Zoe knew what was happening. She didn't know about the stone, but she did know about the domino effect wish chain that was occurring.
She smiled, as she thought of how she could take advantage of this. All she needed to do was make wish and it would be granted to her brother, as if he was the one that had made it.
Jon watched Zoe's lips move again, but since he couldn't hear her voice, he didn't hear her wish. So he wouldn't notice anything different once the wish was granted, just like with the stone.