Well, if nothing else we've certainly learned to call 911 immediately even if we think we will find our missing loved one and it will be a waste of 911 time and we might feel silly or something. When in doubt, call. Call, call, call. MOO.
I think you've got a point. Even if your kid turns up before the police arrive, I think they would rather respond to a well meaning false alarm or jumping to conclusion than have it turn out tragically.