A handy combination that I had to search like hell to find. If a program's window disappears from the screen but it is still open - meaning the window has moved to a location off the screen:
Alt-Tab to the missing window, then Alt-Space, M, then any arrow key. Now move your mouse and the missing window will suddenly pop back onto the screen.
...
-J-Mac
I wonder if I can make an Autohotkey macro to do it. Then I wouldn't have to remember it with my brain.
-dojibear
How's this? Control+Alt+Shift+S to invoke:
...
-ewemoa
When I've had that happen in the past, I kept an autohotkey script on my desktop that would grab the last active window and center it. So I would select the hidden program in the taskbar, and hit the script, but I agree a custom hotkey would be better.
Since abandoning Windows, I don't have a copy to reference, but this may do the trick, anyone care to test?
WinActivate ; grabs the [url=http://www.autohotkey.com/docs/LastFoundWindow.htm]Last Found Window[/url]