There are no sound "devices" in the drop-down menu in the I/O section of Musescore Preferences

Yes, I noticed :-). Anyhow, I get that you might not be able to predict when it's going to happen, but since you are seeing the problem and we are not, the best we can do is suggest things you can try to do to help diagnose what might be going on. So, next time it happens, think about what has happened on your system, since the previous time it worked - whether it installing a new device or program, playing some game you hadn't played in a while, firing up Zoom or some other program that changes audio settings, changing some system-wide settings on your own, etc. If it happens to you only once, you would understandably have no idea which might be relevant, but if it happens often enough to be a concern - and it sounds like it is - it is worth taking notes on what you remember, and the correlating the notes next time it happens, and reporting to us what things you saw in common that might be the issue, Then we can suggest perhaps suggest a course of action for you to try in seeing if you can force the issue to happen.

So unfortunately, tracking down and fixing a rare/sporadic problem like this is going to require some input from motivated users who can help us narrow things down.

FWIW, a good current example of this happening is an issue currently affecting a small number of Windows users who are experiencing crashes on starting after updating. Again, it's a problem none of the developers had been able to reproduce - our updates go smoothly, as do those of the vast majority of users. But eventually we got enough reports from people who were seeing the crashes that we were able to ask relevant questions and eventually figure out some common elements to their usage, and are now fairly certainly we know what specifically is going wrong with the update process on these systems, even though we can't reproduce the problem ourselves. We're close enough to understanding that I'm guessing we'll have a solid answer within the next few days, even though I still don't know what that answer will be. But the point is, it's the help of those users who are willing to take the time to work with us in getting to the bottom of the problem that is essential to these efforts. We appreciate all of you!

MuseScore is open source in the sense of anyone who knows how to program is welcome to get involved in actual development, but at least as important is the community of users who get involved in tracking down problems like this!