There's an option to right click in the systray, and when you choose "send an instant message..." you can send 'to an email' which probably means that this is easily possible if this person has your email. I can't test it not knowing people whos emails I don't have, but that could be the case.
Also, is there a chance they're a deleted contact?
/ 
![[Image: gayspam.gif]](http://shoutbox.menthix.net/images/smilies/gayspam.gif)
