This has happened to me way too many times. I think it remembers being on an external monitor or something and then you can't get to it with a mouse and also the PowerToys FancyZones shortcuts don't work.
Use Shift+Right Click on the taskbar icon for the window and select "Move". You may also need to fiddle the arrow keys a bit if moving the mouse doesn't immediately snap the window to that location.
"Windows" is an awful window manager as it turns out.