I have been in the same situation before. I was walking into a Safeway and I heard this "thumping" and what sounded like voices coming from the trunk of a car. I was tempted to phone the police right then (but I didn't have a cell phone). So I went into the store and got the manager (I had worked there before). We went back out to the car and knocked on the trunk and it turns out there were two little kidsin there. I stayed with the care and the manager went back in to page the owner of the car. We figured that if no one answered immediately the next step was to phone the police. It turns out that there were two little boys who didn't want to go into the store with their parents. So the parents left them in the car and somehow they managed to flip down the back seat, get into the trunk area, but they couldn't get back out.

That definitely left me questioning the sanity of some parents...