Strange as the situation is, it seems like that was jamz and not some rogue admin or imposter, since his address and the one for jamz in my nickname blacklist are from the same UK ISP. Besides knowledge of an admin password, of course. I agree it was unfair, but you might not get anywhere with this one. :/
http://ac.pwnz.org/other/j/
http://ac.pwnz.org/other/j/