You did the right thing. If the kids seemed over-heated or like they'd been there a while, then maybe. I might have stayed for 10 minutes to see if the parents emerged. People are WAY too quick to call the cops. We are way to overly protective of kids.
Totally agree with parents being over protective nowadays. Us kids used to disappear all day and only came home for food and my parents couldn't have cared less. I remember going over a jump on my bike and wiping out onto a broken whiskey bottle. Huge cut on my thigh about three inches long and an inch deep. Rode home and showed my Mom and all she said was "Well it must be summer now if I am taking one of you in for stitches. Get a towel on it and get in the car." edit: I just remembered that I rode all the way home and just before I got there my neighbor Anne asked me what I was doing and I said I was going to go get stitches and showed her the cut. Big tough guy. And then as soon as I saw my mom a minute later I started bawling. Big tough guy.