I think it's weird that this ball has to become some lesson for a variety of people. They caught it, they wanted to keep it. More power to them. If the kid gets it, he learns to appreciate kindness. If he doesn't, he learns he won't get everything he wants. Either way, who cares?
Here's the thing about kids. They give the ball to the kid, he forgets about it 2 hours later and is in the backseat complaining for ice cream. They take it home and he either:
A. Plays baseball and the ball gets mixed in with a bunch of others
B. Doesn't like to play outside and it goes in a garage sale or gets thrown out or chewed up by a dog.
Let's not over-romanticize this on the kids account. I'd rather the grown up keep it and take their stupid pictures if that's what makes them happy. Everyone has so many damn judgements on people.
Also - if this same kid does this in a restaurant, everyone is murmuring about why these irresponsible parents don't discipline their whiny kid.
The people offered the kid the ball, the parents refused. Nothing wrong with that.
Now that I think about it, that's probably the reason why the kid was crying. His parents told him no.