I just wrote and erased a whole long backstory. I think it's better just to give the example that triggered this question:
DD is newly 3. I leave her in the Stay & Play at the gym a few times a week while I work out. Today, as we were driving away from the gym, on our way to Starbucks for a pre-arranged mama-daughter croissant date. Chattering in the backseat, DD told me proudly how she'd used the potty at Stay & Play, and then went on to tell me how another child had a doll she wanted when she came back from the bathroom, so she snatched it out of that child's hand.
I talked to DD about how it didn't sound like she'd been very kind, and reminded her about sharing and taking turns. We practiced the language she can use when she wants a toy that another child has, and I reiterated that she may just have to find something else to play with.
I was initially tempted to tell her that we couldn't go to Starbucks because she shouldn't get a treat if she couldn't remember to share, but I didn't because she's only three, so her stories are often not reliable. If it happened how she said, I want to trust that the teachers at Stay & Play addressed it then, but it's also possible that she was recounting something from another day, or another setting, or several events blended together. What do you do when LO tells you about misbehavior that occurred when they were not under your supervision?