Wednesday late morning

This is a mystery.  When Grandma throws one of those cool white balls, I see where it falls and chase it.  And I dig and look for it in the snow...but I can't find it.  After a while, I look back to Grandma and low and behold the cool white ball is at her feet ... and she throws it again ... and I chase it ... and I can't find it ... and I look back ... and the ball is at her feet again.  How does it get there mama?  I need to know.