This happened to me as well but with a dentist. When I first moved to Boston I had never had any cavities but my new dentist kept remarking about how great my dental insurance was - I was in the insurance sweet spot of under 26 so I was covered by my mom's policy as primary and had secondary coverage through my dad's policy and my school's policy. Well wouldn't you know, I averaged two cavities a year during law school even though my brushing & flossing habits were unchanged.
When I finally graduated and switched to a dentist closer to my office I insisted to my new dentist that I had had six cavities filled and he insisted that I most definitely hadn't. There wasn't a single filling to be seen on my x-rays. Dentist #1 had been scheduling me to have a cavity drilled after every regular visit. Apparently he was just giving me a shot of lidocaine and pretending to drill in my mouth for an hour so he could bill my "great" insurance.