The answer is unknowable, as it depends on how well your phone and the phone or phones that "bounce" the signal can connect. A phone sitting on a car seat will connect better than one that's in the car's trunk. A closed trunk will interfere with radio wave signals too, how much will depend on the type of material (steel? aluminum? fiberglass?) used in the trunk lid. This will apply to all involved phones, and those phones' circumstances are unknown.
I assume there are a lot of parking spaces in the garage. Do you plan to stake out each occupied space and confront every driver, or follow every car that leaves the lot? With no more specific information, even an interested police department would have little to go on. Confronting the driver or following the car will expose you to personal risk.
With no disrespect, I would gently suggest that your hopes for recovery are misplaced.