How to move unseen windows => Cannot access my application after switching monitors

On Windows 7, with the hidden application focused use Windows Key + Left or Right. You will need to press the arrow key several times.

For earlier versions as well as Windows 7, press Alt + Spacebar to open the hidden application's system menu, then the letter M to select Move, finally arrow key. This will lock the window to your mouse, now move your mouse to the position you desire the window.

Self answer.

I kept searching for a way to do that... almost at random I clicked on the Desktop icon besides Start button... And all my wandering windows came back ;-)

So the answer is click the desktop shortcut. (or shortcut Windows + D).

In my search I found a nice site however that list all possible key shortcuts for windows. There are some I had never heard about, and that I might start using.

I found a ever more complete list of short cuts, working for windows, but I also saw some for mac. A breef look let me think it was a good link to keep. Wikipedia lists of key shortcuts.