Somehow, I hit Windows | Zoom Toggle and lost my file tab captions. I had to search the internet to find this. I propose:
1) An indicator be set on Windows | Zoom Toggle to show this feature is active. I probably would have found this directly if there were an indicator.
2) Reset Window Layout should reset Zoom Toggle to be off. That was the second thing I tried. If you think about it, it's expected behavior that resetting the Window Layout should turn this off.