To be frank, crypto-disappearances are not likely, but if they really happen, they are triggered by a dead internet connection or the collapse of the electricity network. If such an occurrence is indeed, there is definitely no need to think about it. There's just a way back to waiting for power and internet maintenance. And we can use the crypto that we have as well. Even if actually crypto vanishes right now without any reason, it won't create a global crisis. Because the number of world residents with cryptocurrency is very small.