It does sound strange. I had the same thing happen to me, in fact few days ago that SSD wouldn't show anywhere, actually I was able to pull the ssd in device manager but with 0mb in exFAT and it was only for brief moment and after that don't matter what it was gone.
The fact that you can record RAW its something else..
What you could do is try loading that SSD outside Windows, through Hard Disk or Partition Manager or any life CD e.g. Paragon, EaseUs or even Ubuntu and see if it shows, sometimes windows wont show but these software can and you could formatted that way and if its not dead it might fix it.
Now I'm curious myself.