David Copperfield may be able to make an entire house disappear, but missing windows are an event that nearly everyone has encountered. This occurs more frequently with laptops, as they frequently change profiles that have different video outputs (especially if you use a docking station). Some programs save their last window positions, so if you opened a program when you were docked, then the program may open off-screen when you are undocked.
Your program windows are still on your desktop; but you just can’t see them. Most people have gotten so dependent on their OS’s graphic user interface, that they can’t understand how to interact with something that cannot be seen. Never fear, because I am here to gift you with second sight: how to see what cannot be seen.
Most likely you can see the running program in your taskbar, but cannot see its corresponding window.
This trick has worked ever since Windows 3.1. Back then I would intentionally move the windows of cute secretaries off-screen so they would be forced to call tech support, which allowed me to flex my L33T 5KiLL5 and impress the ladies.