A former neighbor in San Diego was working in the Naval Investigative Service, and he was surprised that the local PD weren't going to try to find who stole his motorcycle. He found the guy in a couple of weeks, got his bike back, and guy did some time in county. A few months later his bike was stolen again, and on a hunch he tracked down the same guy, who did it to prove that he could get away with it. As I recall the thief ended up at a state prison.
As far as what would I do if someone called asking for information, I don't give out information on others over the phone, or in oerson to anyone who is not authorized to gather such information.