Sorry to hear about the dealer, some are great, some are terrible. I always tell my dealers with all my vehicles to never wash the car.
As for the rear wiper, mu guess (GUESS), is that when they swapped out the module, the tech forgot to connect the rear wiper switch connector to the switch when the center panel was re-installed.
Just a guess, but sometimes the easiest is the most probable cause of a problem.
If you want to check, pull the center panel off and see if the connector is connected to the switch.