Webchances are the gps unit was put by a previous dealership before carvana, and it's just been left over in the car and not seen by anyone. You might want to use a mirror to check the undercarriage without lifting the vehicle. Some trackers are magnetic and can be quickly placed under a car.

Webi know this is old, but they absolutely do install a gps tracker with remote kill. Just google it and you even get the carvana installer instructions.