The person who grabbed for the stone was Jon's mom.
She looked at it. "How did this get in here?" She put it back on the nightstand and got out of bed. She figured it was something from her children that she grabbed from downstairs and put there before she went to sleep the previous night. She was really tired at the time, so that's probably why she couldn't remember doing it.
She stretched and began to get ready for the day.
Meanwhile, Jon was getting ready for school himself. He had decided to wish for something after he got ready for school, but now he changed his mind.
He walked back into his room and grabbed the stone. "I wish ..." he said, not realizing that the wish would be granted to his mom, instead of him.