Something to look out for if it come back...
Seen some posts out there where people saw this from their car stereos and the Bluetooth connection. So if see it again, see what type of Bluetooth connection and potentially what the options are under it (Settings > Bluetooth > device > info circle. If car stereo, there are options under there that might be affecting the screen. Have not see in any of my cars, but maybe due to one has an old car connection and the other is using CarPlay which is cabled.
Might not be car but thinking along the lines of speaker/soundbars or other.
Also, might be something going on with a false driving Focus turning on, but doubt that since the home screen is not showing an icon for Driving Focus. But if somehow getting false enables, can switch that Focus to manual.