When you unplug the phone from the car, Waze will stop the current navigation and forget the route.

This can happen for a variety of reasons such as making a pit stop, or even a flaky usb port.

If you need to continue the route, you need to re set the destination, and for this you need internet access. If you are in the middle of nowhere with no internet, you are screwed.

Google Maps doesn't forget the current navigation when the phone unplugs from the car. The navigation should be stopped only if the user stops it manually.