This stone looked nearly the same, but it wasn't. It was the Random Stone. And because of the small crack running through it, the wishes made with it wouldn't necessarily be granted to the wisher. The stone would pick out someone within 50 feet of the one who made the wish and grant it to him or her instead (as if they were the ones who made the wish). It was completely random as to whom the stone would pick. And as with the original stone, only the wisher and those who heard the wish made would notice the changes in reality.
Zoe walked towards the spot where she usually met up with her friends before school. And as she approached Athena, she took out the stone, completely unaware that it wasn't the same stone she inherited from her grandfather.