Li Fan and the others were rescued by Zhang Jiugao and brought back to the mountain when the sect leader dispatched a team led by Nascent Soul masters to search the mountain. It was only three days later that they found Lu Yu's corpse at the bottom of a ravine about a hundred li from the tomb.
A hundred li away, a sword light can bridge the distance in a blink of an eye; therefore, it's hard to determine whether he was ambushed, his body dumped, or killed in a swordfight in the sky before falling to that spot.
Of course, when Lu Yu was found, all his magic artifacts, storage jade pendant, the Lu Family's mechanism for hiding items in his right arm, and the four dragons tasked with guarding him were all gone. Whether they were plundered by his killer or taken by a passerby seeking treasures in the Buzhou Mountain as a 'fortuitous encounter' remains unknown.
