Well, as others have said in past threads, the landscape was totally different and constantly changing. You might want to travel to that village near the spine of the world and, Oooops! its on top of a mountain! You weave wouldn't work then. So since you can't use it you loose it. Although I agree that it seems pretty lame that it was forgotten. Even if every scrap of word written for 300 years was destroyed someone STILL should have made a record of the weave and how it was done. Even for the male half.