I believe the SD card must be ordered specifically for the car VIN, not just paired by the dealer. The cards are rather expensive so dealers sometimes remove them from cars on the lot and forget to reinstall it when the car is sold. The missing card will affect some functions of the unit (more than just missing maps). If the navigation unit will not keep radio station and phone information after you solve the SD card issue, look for a failed or missing fuse. There is a separate circuit that supplies continuous power for the memory while the car is parked.
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015; traded 8/10/2019 at 82,436 miles
White LEAF 2019 SL Plus purchased 8/10/2019