Meh..i have said it before so ill say it again.
All you need is a gun to get a gun, if anything "this bad" does happen there will be plenty of corpses to loot weapons ammo, cloths (bullet hole and blood ridden of course) and food off of.
Avoid all humans, hit hard and fast,loot and beat feet. Rinse and repeat as long as you carry wind in your lungs and take your naps above dirt.