Im a bit confused, at the point the police attached the unmarked tracking device on the suspects vehicle, did the suspect not obtain possession rights to the tr

Im a bit confused, at the point the police attached the unmarked tracking device on the suspects vehicle, did the suspect not obtain possession rights to the tracker? If not can the police just attach a device to you vehicle then charge you with theft immediately? How did the removal and subsequent storage result in theft if the device was already in the suspects possession?