I have heard the same that these theives actually went to a lot of trouble to get to the dogs. A few years ago my mums old collie x escaped from my brothers house whilst my mum was on holiday. We treid everywere then we were given the number for a small rescue centre nearby. I remembrede that this was were the dog had come from many years ago. We phoned and she was there she had been taken there as she still wore on her collar a tag from when she had been in the rescue. When we collected her we asked why she hadn't been scanned. They said they hadn't bothered as their scanner was broken and they didn't bother taking her to the vets to get them to do it. A chip only works if the vet or rescue that find them bother scanning them. I was also told a chip can be over ridden when a new chip is inserted by some one who chips dogs.