First off, I must state that I should know the answer to this question, but sadly i don't.
Im trying to aquire a Woodsmens Guild Headquarters, but I seem to be failing. Im quite certain that no other nation has aquired this building already, as I own half the world and have various agents throughout the other half. Also, Ive been training many Retinue longbowmen and Sherwoods for quite some time now, and still nothing.
Anything else I can try?