Not really an AIBU but more of a WWYD?
Where I park for work is not the nicest area of town: lots of private-landlord-owned back to back terraces, many not in a good state of repair. To get from the car park I have to do a loop round a square, off which there are several cul-de-sacs of terraces, and these tend to have a gate across the end of the road.
Anyway, as I set off for home yesterday I rounded one corner of the square and came nose to bumper with a toddler in the middle of the road. Luckily I was driving very slowly. He can't have been more than about 24 months. There was not an adult in sight. He moved out of the way, and I parked up in the first available space, got out and went looking for him. He was on the pavement by this time, heading for the grassy area in the middle of the square. Still no adults in sight. I went up to him and said "Hello, where's your mummy? Shall we try and find her?" Of course poor kid didn't say anything.
I kept looking around and then saw that coming out of the terrace opposite, very slowly and casually, was a teenage girl (but prob only just, she didn't look more than 13) with two younger school-age children. I noticed that the gate of this street was open. So I said to her "Do you know this little boy?" She said yes, so I said, "I just found him in the middle of the road, I could have run him over." She said "Thank you", sounding quite concerned, and she went and took the toddler by the hand and started leading him back towards the terrace. At that point I drove away.
I keep wondering whether I should have talked more to the girl, asked her who she was (sister?), asked her where the his/their parents were, checked to see which house they went into. What would you have done?