Have a hunt around unusual for the wiring to be gone, just drops down towards the rear light. Take the access panel off the rear light and look around to see if it is there. When you find it you could drop some string down the inside of the panel from where the light unit fits and tie the wiring onto the end. This will help pull the wiring back up to the light location. Replace the light unit and wiring. May even get the vanity lights to work.