There were a few names I wanted that I knew would go in a hurry when I found it to be the prime time to start my guild, if that were to ever occur (hey we all sort of want that don't we?) and unfortunately they were taken. Yet I have not seen any of them on the game. So per Jack it is entirely possible despite the fact that they are not in the directory that they are already in use even if there is only one member. In addition, they could have taken the name you requested out of the possible names to be requested so it would say it was taken automatically for the next person who requested the exact name. Usually if a guild name is taken it will tell you right away.