The problem with gold is twofold.
1) If the world's currencies did disappear catastrophically, the over-valued gold would also decrease dramatically in value. This is because currently there is a surplus or bubble of currency, which is what a fiat currency is. You just invent the value as you go along. More people have more of it, so everything is much more expensive, but that does not mean value. Were a real world-wide currency disaster to happen, gold would quickly reset to something more realistic, depending on what people would pay. Say around 100-200/per ounce. This leads to point 2.
2) Gold has little worth to survival. It only really obtains serious value once a stable and agrarian society has been established, because you begin to have classes and social stratification where it doesn't make sense to hoard more wheat than you need, and you don't need to trade anything. Then gold becomes useful, but it is still a fiat currency with an invented value. If Hawaii ever became really isolated again, gold here wouldn't be worth hardly anything. You would need many, many years for things to re-stabilize.
The most valuable things in any real shtf situation are going to be survival related trades. That's why kings started out as warriors, they were the best survivors, and provided the most for their people. Anyhow, all in my opinion
