You'd still have a telephone number. From that telephone number you could go to a judge and request a warrant for the telephone records. From there you could lo

You'd still have a telephone number. From that telephone number you could go to a judge and request a warrant for the telephone records. From there you could look at all the numbers dialed and received. Now you get a warrant for the addresses of the subscribers. No bulk surveillance required, just honest police work within the confines of a valid and acceptable legal framework.