UPDATE#2: I've taken to recovering from this failure mode by unplugging the blanked monitor's HDMI cable and plugging it back in multiple times until the situation corrects itself -- which it seems to eventually do. I am a bit concerned about wear and tear.
A big concern here is there doesn't seem to be any obvious way of narrowing down which of the many moving parts are the right place to lodge a bug report.
UPDATE#1 The following screenshot is the most frequent failure mode following return from screen lock:
But I seem to be able to recover my configuration if I power the system off in order to restart it.
Original:
When i leave my 3-monitor computer long enough for my monitors to blank, when I then press a key to log in, the only monitor that i can use is the smallest one. The other two remain off. When I log back in, and the desktop reappears on the smaller monitor but the two larger monitors remain off. When I right click to discover what has happened, it is impossible to properly get back my 3 monitor configuration, so i have to power off and restart the computer. When it comes back, all my web browser windows are on the smallest monitor although the other two monitors have come back. I must then rearrange my desk top, moving my browser windows to the larger monitors and expanding the browser windows.
Also, note the screenshot says "No proprietary drivers are in use." 
This is 22.04.2 LTS with nvidia driver metapackage 525 (proprietary) NVIDIA Corporation GA104 [GeForce RTX 3070 Ti]
One problem, but not the ultimate cause of the Title's symptom, was a variant of the nvidia install issue with the most recent driver and ubuntu version reported at:
https://forums.developer.nvidia.com/t/ubuntu-and-nvidia-provided-packages-conflict-breaking-installation/259150
However correcting that situation only made the problem less reproducible. It is still happening.
One other strange thing is when I restart the system, although sometimes it corrects the situation, at other times it will present me with all 3 screens during login, only to, upon login, collapse down to only 2 screens:
If I add the 3'rd screen (which is display 1):
The Apply doesn't present me with the corresponding configuration, but rather only 2 screens which, when it reverts becomes a different 2-screen configuration:
After almost a week of trying all sorts of paths to reinstall Ubuntu so as to get the 3 monitor situation working, I've got my system running again but I can't be confident that it won't start failing again. Something is seriously wrong with the latest Ubuntu installation process at least w/regard to my hardware configuration.
