Of course, there are LOTS of JWs who work in insurance or at hospitals or medical offices transcribing medical records, and coding for insurance billing, so I imagine even a discrete JW could be outed.
Years ago a few sisters who worked for Stanford Medical routinely & secretly informed Elders about any JWs who took blood, had abortions, had STDs, smoked, and single sisters on birth control, etc, etc. The "Guilty" never met their accusers or had any idea how the elders found out.