The person who grabbed for the stone was Karyn.
She immediately recognized it, or she thought she did, anyway. It was Jon's wishing stone. He must have left it here by accident, she thought. Part of her thought that Jon left it on purpose, but why would he do that without telling her about it?
She held it in her hand and thought that she might as well make a wish since she had the stone. What harm would it do, even if it was just a small wish?
She smiled when she thought of something. "I wish ..." she said, not realizing that her wish would be granted to Jon, instead of her.