It is very vulnerable without a state behind it
I'm not buying that. Transporting gold from place to place is extremely vulnerable to brigandage. Storing gold anywhere makes it vulnerable to robbery. Bitcoin, not so much; it's up to you how secure or insecure your bitcoin are; there are no physical limits. I think using gold depends on the state much more than does using bitcoin.
Without Internet all your bitcoins instantaneously become just digital garbage. Gold is not perfect, but it has been around as a means of exchange and store of value for almost five millennia...
How would internet disappear?
Just unplug your cable or turn off your wi-fi router. As easy as that...