Re: the free registry - does your dog have a tag or something with a phone number for that particular registry? The thing is, the finder that scans and tries to trace the chip has to contact that registry to get the information.
I know AVID gives a plastic tag with the microchip number imprinted on it. Those things break, and numbers wear off.
I had rescue tags made with my phone number that went on all rescue dogs when they were placed, as a backup - if the owner was away, and the pet got lost, I could be called and retrieve the dog until the owner returned.
I ended up having stainless tags also made up with the 800 number for avid. I just didn't see those plastic tags holding up over the long haul.