Send the DV to West ASAP CMRRR. I bet that either the OC hired West and dumped NCO or NCO resold the debt to West. I suspect the latter. If you don't DV West within the 30 days, you'll likely see then on your CR shortly after the 30 days.
If I read you right, you disputed through the 3 CRAs the NCO listing. By law, they have 30 days or so to respond to your dispute or they must delete it. If 30 days passed, you might want to pull your reports.
In general, if you DV a CA and that CA disappears, then the OC can get a new CA, or it can be resold from CA to CA. This can go on and on and on, past SOL and past the 7 years. However, you can't get sued and if you dispute the CRAs past the 7 years, then the CRAs would delete.
I wrote "in general" because in many cases state law can trump fed law in matters like this. You also have HIPAA on your side here and you can always get them on violations due to medical privacy, if any happened. Maybe others could chime in here.