On my Ubuntu 14.04 with the default unity dock, the Skype application is a big blue icon in the list. Right clicking it gives me a popup menu with three main windows listed, one named after the current chat, one for File Transfers, and one for " - Skype". Click that last one seems to activate the main contacts window.
If it is then offscreen, you may need to press alt+space to open the window's system menu, then hit 'm' to select Move, then wave the mouse around or to the edge of the screen (to activate 'glue to screen edge' behaviour) to force the window to reposition itself onscreen. I switch between multiple monitors when I move between two work locations and my windows frequently get stuck offscreen.