i just thought you could see if someone is invisible in skype, if you just delete (reset) his profile picture. Because i know if you install skype on a new device the profile pictures are saved only if he is online (or invisible). That means if i just want to so if someone is invisible you just delete or reset his profile picture and if you see after a few seconds his picture again = he is invisible.
BUT... i don't know where the contact picture are saved on on my mac (running mountain lion). I just couldn't find theme... so if you know where they are saved, would it be great.