I ran this same adventure as the first couple of sessions for my pulp campaign. The players were forced to flee from the cavern without capturing the opium lord, although they did manage to seal part of the cavern with dynamite. When they returned to watch the authorities "clean up", the big bad had escaped out the back with the celestial jade and the prototype jet engines. They are still hunting him! I will send my players the link to your site, I am sure they will enjoy reading your recounting of the adventure.