(Just for Windows.)
If for some reasons your application windows may fall out of visible screen (mostly notably when changing from dual-monitor screen to single-monitor one) and you can’t find them back, try a utility called SheepDog. Run it, press
Win + W to re position off-screen windows to top left of your primary screen.
It’s free to download at http://sheepdog.codeplex.com/, also it’s open-source.