The dog experiencing this scenario is unable to return because they have entered a vehicle or object that has moved and is now in another area outside their home territory, the area where they escaped or were occupying.
This scenario is very rare for a dog. When it does occur the most likely situation encountered is the pet owner’s vehicle or other property is stolen from a public place and the dog is in the car. Eventually, many of these dogs will show up out on the streets as they exit the vehicle or are turned loose.