Oddly, I heard a story today of a dog lost in Kentucky, hit by a car, landed in local high-kill shelter pulled by rescue in PA then sent to a foster home in Philly to heal for adoption. Only after a routine vet visit by the foster did they even scan for a microchip to check if the dog (9 y/o beagle) had an owner. If the shelter had scanned the dog on intake or at any point, the dog would have been home 17 months (!!!) sooner, so in addition to not being GPS, they have to at least be checked for, which apparently isn't as common sense as I thought.
Max "the ninja"-American Cocker Spaniel G-day 3/2009
Charlie "the middle child"- Orange Tabby G-day 7/2005
Sadie - Grey Tabby 9/1996-8/4/2012 RIP