Not strictly true. This has been tried before in places like Serbia during the civil war. Even in total societal breakdown, gold and silver retain their value while fiat turns near worthless overnight. You can get anything you want: food, weapons, ammo, medicine, hygiene products, a helicopter ride out, etc, if you have gold. Granted, being able to defend yourself is a prerequisite to trading in such a situation, but gold is the ultimate store of value.