You're right.
Some rudimentary testing shows that the ^ prefix does not seem to work with on DISCONNECT.
*sigh*
Update:
Aha! found it. /help Halting default text:
The ^ event prefix currently works only on the following types of events:
ACTION, BAN, CHAT, DEHELP, DEOP, DEVOICE, HELP, INVITE, JOIN, KICK,
MODE, NICK, NOTICE, OP, OPEN, PART, PING, TEXT, UNBAN, USERMODE,
VOICE, QUIT, SERV, SERVERMODE, SERVEROP, SNOTICE, TOPIC, WALLOPS.
Some stuff in the help file is hard to find. Had I seen that first...
