Prepper Stash: The Holdouts
Find this stash at the Elliot Residence, south of the FANG Center in Jacob's region.
The prepper note is on some ammo crates out in the front (south) of the barricaded house.
The front door is open, but won't lead you to the stash. You can find a shotgun there, and some ammo and knives. There's even a fishing pole, if for some reason you don't have one yet.
To get on the stash trail, go around the back of the house. Climb up on the awning, and enter through the window below the 'B' in 'JACOB.'
There's a collectible comic just inside.
Pass through the bathroom and right out the far (south-east) window.
Turn right and re-enter the house through the other window here.
Take the stairs down to the kitchen, where the bunker keycard will be on a lanyard on the floor.
As you return outside, three hostiles will drive up to cause trouble.
They've got nothing going for them here, so wipe them out, then proceed to the flag-draped shed out back.
Shoot the lock off the bunker door, and proceed down.
Unlock the door to gain stash access, and complete the location.