If it saves just one hour in locating the body.
As cruel as it may sound on the surface, I still say go wake up a judge and convince him you need the search warrant for the info. What is merel;y upsetting today most likely will become "an emegency" tomorrow because it allows cops to go charging about telling someone what to do, and because it shuts up the emotionally distraught by proving the cops are "doing something".
Access to the information is generally useful, but based on published reports of how quickly an abducted person winds up a murder victim I do not forsee this having a significant lifesaving impact. The mentally disoriented usually wander around for quite some time without falling into the hands of depraved murders/ kidnappers just looking for (usually) elderly and (usually) non-wealthy victims. And there are products for sale that track the mentally disoriented - go buy them and leave the phone company alone to screw up my service without interruption from Johnny Law.
Evil happens. People do not like evil, and do not like it when evil strikes that closely. But dreaming up laws that only make you feel like something is being done, as opposed to doing something in time to prevent evil from happening, is just that - it makes you "feel" like something is being done.
(Let me catch my breath for a moment.)
OK, now we can go on to discuss all the potentialities for abusing the law.
....
There, that took quite a while, but we covered at least the surface of the slippery slope.
stay safe.