I did not share my Passcode, Apple ID or Password.. I think The Find My iPhone was not turned on basically, I'm not sure but I did not find it in the list of Find My iPhones after it was lost.
It was stolen from home by a housemaid who was caught while working at other home as video camera picked her trying to steal other mobiles! The housemaid service office confronted her and restored my iPhone that she sold to a mobile trading.
I'm not sure how they were able to do factory reset while they don't have any access ! Perhaps there are software that do so.. Is there ?