Skiptracing:
Skiptracing (also skip tracing, or debtor and fugitive recovery[1]) is the process of locating a person’s whereabouts for any number of purposes. A skiptracer is someone who performs this task, which may be the person’s primary occupation. The term “skip” (as a noun) refers to the person being searched for, and is derived from the idiomatic expression “to skip town”, meaning to depart (perhaps in a rush), leaving minimal clues behind to “trace” the “skip” to a new location. [Wikipedia]
Noted in an interview with Frank Ahearn, NewScientist (24 June 2017):
How did you become a “skip tracer”, finding people who have run out on their lives?
I was doing undercover work for a detective agency in the 1980s when I saw the skip tracer at work and it fascinated me. I told my boss I wanted to do the job, and he said, “Sure, if you can get me a copy of my phone records.” That night I went to a payphone, called the phone company pretending to be my boss and said I needed to go over my calls. They told me every place my boss had called in the last few months. The next day I became a skip tracer.
I got really good at “pretexting” – essentially tricking people into handing over information. Later, I had my own firm of skip tracers.