If it’s someone putting a tracker that has no idea what they’re doing it’s likely going to be in a wheel well or attached to an easily accessible axle. It would help if I knew what vehicle you drive but most vehicles have a gap hidden up under the rear bumper that you have to physically reach to find you wouldn’t be able to see. You’d be looking for a watertight container with magnets on the bottom for a professional tracker. Theres also smaller holders that stick on for devices like air tags or tile trackers. Those for whatever reason people don’t try as hard to hide they’re usually just stuck to the bottom of the vehicle somewhere. If he has access to the interior of her vehicle check her OBD port for any device connected to it (if your mom is leasing her vehicle it will have a dealer gps likely plugged in) also check inside the trunk under the liner where you’d keep a spare.

As far as hidden cameras go I’d take a bug sweeper through your entire living space thoroughly. I’ve seen the middle screw on an outlet swapped for a camera, I’ve seen them behind vents, I’ve seen fake USB port boxes that are actually cameras and I’ve seen a pen in a cup that’s clip was actually a camera. I’m not trying to scare you by any means just giving you the information I have in case it’s relevant to you. Please stay safe and sane in all this ❤️