O.K., we now know that some of the Cubs fans bring balls with them to the outfield seats. This allows them to keep the opposing teams HR ball and throw the one they brought back onto the field. And keep face with those around them to throw it back.
What I'm wondering is the quality of the ball(s) they throw back. What is the likelihood that a junk, but pristine ball makes it back into the rotation? But, the pristine ball isn't a MLB ball. Could be a raised seam youth ball or a new practice ball. Any chance this has ever happened?
My guess is that any ball thrown back now is either given to the HR hitter or thrown out. But, years ago, before anyone knew people brought their own balls, who knows???