Yes, eventually precious metals will lose their value, but there is a critical period during a collapse when fiat currency hyperinflates virtually overnight, while precious metal will gain in value substantially. It won't last, maybe only a week or two, maybe a month, depending on how quickly individual surpluses are diminished, and people are left only with what they feel they must have. That's when gold and silver markets will fall. Those two or three weeks are when you can catch peddlers who, being unwilling to do business in dollars, will still want some form of currency they can recognize. Business owners will want to try and continue unloading stock, so they will fall back to something. They'll look to something easily recognized as currency, and for a time a person with some junk silver or some gold coins could probably find some really good deals.

Consumables, such as food and fuel, will likely quit trading in anything but like kind once the local surpluses get depleted and no restocking occurs. That will be the turning point for precious metals. Since just in time restocking is a SOP for all the big stores, they have at most 3 days until their shelves are picked clean. But it will take some time for that to spread into the rest of the market.

At some point, the economy ought to recover, maybe a matter of months, maybe years. When it does, there must be some form of currency that people can rely on. No one will want a fiat currency again, so a standard will be adopted. People with level heads during the crash will be in a good position when the recovery starts up.

It won't last, but there is a window of opportunity, and a prepared person could capitalize on the situation to great effect.