A spectator found the baseball of Shohei Ohtani's first home run in the bleachers.
According to the linked article, she was surrounded by security and pressured to give up the ball (so that Ohtani can have the memorabilium). She was offered other memorabilia as a compensation.
There are two somewhat connected legal questions here (I hope it's OK to discuss them together):
Who owned the ball? Was it actually the woman's? My own legal assessment leans to "no" because no transfer of ownership was intended and the ball was probably not "abandoned". On the other hand, baseball customs and precedence may be that a spectator acquires ownership.
Even if she didn't obtain ownership: Was the security staff allowed to keep her from leaving with the ball? That situation created a lot of pressure to make a decision which may not have been favorable. Let's assume she was willing to pass on an ID so that she could be contacted later to resolve the dispute.