We know that Master Park studied Tang Soo Do when he was younger, and then transferred to Bagua, and only studied Bagua under one teacher, Lu Shui Tian. Blue Dragon Kung Fu's website explains the lineage a little, and indicates there are two unknown elements:
The only written records of the origination of Ba Gua Zhang can be traced to Dong Hai Chuan [...]. However, Lu Shui Tian first learned from one, Li Qing Wu, and stated that his Ba Gua Zhang did not come from Dong Hai Chuan, and was at least 500 years old. In fact, he believed what he learned from Li Qing Wu was much deeper and complete than what he learned from his second teacher, (believed to be Lu Shui Kui, though unconfirmed) who was a Fourth Generation lineage holder in the Yin Fu lineage under Dong Hai Chuan.
So the question is .. How do we trace the lineage, up from Lu Shui Tian? Where does Li Qing Wu's Bagua come from? Who was Lu Shui Tian's second teacher, in the Yin Fu lineage?