"Whoa," Jon said.
"What is it this time?" Karyn asked.
"I ... I remember Zoe. This is too weird." Memories of his previous Goth sister cascaded through his mind, changing his already-existing memories into new ones (or rather returning them to what they used to be before Zoe disappeared).
"Who's Zoe?" Athena asked.
Jon just stared at her. "What do you mean? You were the one looking for her. Don't you remember?"
Athena shook her head.
But then Jon realized it was because of the necklace. Athena was being affected by the wish that made Zoe disappear. So now, Athena didn't remember Zoe any more than anyone else, except for Jon, who was wearing the pendant necklace.
This anti-magic necklace was making things confusing, but Jon was still glad that he had it.