Sometimes it can happen that an application window may get “locked out” of the visible area of your desktop. Especially when you are extending your desktop in multiple displays and later on one of these displays is disconnected, a program may keep positioning its window in the good-old coordinates it had when it closed, even if these coordinates are not inside the accessible frame any more.
And this is where the move-window-by-keyboard feature comes to the rescue, a feature that I guess most people never ever use, as most of the time we use the mouse to move windows around the screen.
Locate the window that you need to bring back on the Windows taskbar, at the bottom of the screen. Then right-click on it while holding the Shift key down. You must be able to see this context menu:
It is very important to hold Shift pressed while right-clicking because if you don’t, you’ll get a whole different menu, which is not the one you’re looking for:
Click on “Move”. After clicking on Move the hidden window should be already focused and movable using the keyboard. Use your keyboard’s arrow keys and within a few seconds you will be able to drag the window with the visible area of your Desktop. When you can see the title bar of the window you can leave the arrow keys and continue with your mouse.
I hope this helped!