WHERE IT STARTS:
The Treasure Hunt starts at COCO'S CONUCO OVEN, SOMBREADO GORGE, CONUCO.
THE NOTE SAYS:
They've found me out. The soldados are coming. I won't be able to help you anymore.
The supplies for La Moral are in the oven storage room. I locked it up and broke everything so the only way in is through the fire.
Use my generator to get in. I don't think the soldados will figure it out - but you will. Viva La Moral!"
WHAT TO DO:
Written guide below the Walkthrough Video
After reading the note, go into the house behind the orange box and unplug the two cables to the orange power generator.
Then go outside to the power generator and push it down into the hut by the blue water tank. Will take a while...
Now you can open the water valve and the fire is out.
Enter the builing where the fire was. Go to the ventilation window. From there you can shoot the lock off the hatch on the ceiling.
Now you can enter the room through the hatch in the ceiling. The keycard for the locked room with the chest is hanging on the wall.