A foul ball trickled down the third-base line which led to this young Athletics fan receiving a very cool souvenir ... for about four seconds.
Yes he threw the ball back on the field. And yes the person who retrieved it appeared to give it to someone else. But, really what would you expect. The third base coach tossed them the ball, so the young fan was simply tossing it back. That's how a game of catch works. How was he supposed to know that in the big leagues, people throw you the ball and let you keep it.
Hopefully someone gave the kid another ball so he came away with a souvenir and a memory.