I think that idea about changing the MOTD was the best one, but if you don't have permissions and can't mog mail... and don't have any out of game way to contact the player... Yeah, it sounds like you're pretty out of luck, sorry.

If there's anyone else that can change the MOTD you can ask them to do that, or ask officers if they have the leader's contact info.

For future reference, it's always a good idea to get some of the higher ranking people on your Skype contacts list or whatnot.