If you stole the phone, or lost, in any case, you must contact the ATS.
In any case, they will search, and the private investigator (if he has good connections in the police department) will only help to find him quickly and return the rightful owner without any extra delay. After all, without a militia, a private investigator will not be able to seize it from, say, a person who bought a telephone from a thief .... And if the militia already even determines who has the stolen telephone, then it’s not always his (new owner of the telephone) for excessive workload (from my personal practice) he will quickly find - this is where a private investigator can work.