I'm new to Ubuntu. I use Skype and often the main window just disappears from my desktop. The Skype instance itself is still running in the background. I know this because I can see its notifications on the bottom right side of the screen.

If I click on the Skype icon again, Ubuntu will launch a new instance instead of maximizing the running instance. Of course this will not work because Skype will not let you sign in: Another instance of Skype may be running.

How do I refocus/bring to the foreground the existing Skype instance? In Windows, you can restore running instances through the taskbar. I've tried cycling through open windows, but the running instance window is no where to be seen.