I know, it's old but...
Yeah sorry for kinda bumping this.
I found out how the servers could be re-listed again if you want them to!
I have tested with a command called "sv_master_legacy_mode" which if set to 0, will re-list a server back on the GMOD 9 server list.
I have put it in like this in my gmod 9 server.cfg file:
sv_master_legacy_mode 0
heartbeat
The reason for the heartbeat is for the server make the server visible on the list.
Warning: It must be put in on the dedicated server, not the client! Also must be at the bottom of the cfg file at all times to work!
Double Warning: I don't know if it will work well... Server I was hosting to test this did appear on the "internet" tab but maybe it is just because it is LAN.
EDIT: It seems it has a bad case of doing a "Your version does not match the servers. Please restart." Error if you try connect directly. You must copy the IP from server information and use the connect command in console to get around it.