This is a very real fear every dog owner and lover has. I will need to look into the rules here where I live. All my animals are microchipped, but they don't live in their collars! First as I crate and rotate with the wire crates, collars can be dangerous to the dog when crated. So the collars come off when in our home. But things can happen!
Like today, just an hour ago, I walked out my front door to go to my car, and there was Razzman, running happily up to me
He was supposed to be in our gated/fenced backyard, or in the house.... Our gate had come open and neither hubby nor I knew that it had! We used to lock our gate, but have slipped out of that habit, which we will go back to now!