If you usually use two monitors in a dual screen setup you may find that when you move back to one (such as when you undock your laptop to go mobile) occasionally some windows disappear. On launching an application it may not appear despite evidence of it running fine (icon in the toolbar for example). This is because the application’s window has opened up in the area of desktop previously visible on your second monitor.
To resolve the problem:
1) Give the application focus by selecting it in the Windows Taskbar or selecting “Switch To” from Task Manager.
2) Press “ALT” and “SPACE” together, which pops up the window context menu.
3) Select “Move”, and then use the arrow keys to move the window into view.
This happened to me again this week and I always forget the keyboard shortcut to launch the current window context menu. Here is a useful link I found that lists useful keyboard shortcuts.