???
It's a safe place for the units of cryptocurrency identified by it, but those aren't money until it can be exchanged for something. Between you burying that USB key under the old oak tree and you digging it back up post-apocalypse, those units of cryptocurrency will have a very different exchange value. It's no different than tucking currency under a mattress, except that the odds of your 2023 cryptocoin being worthless by the time you pull it out is much higher than that the 20th century's global reserve currency becomes worthless. Although it might go the other way, your wallet contents don't sound like a very safe store of money at all.
These completely mindless dunks on crypto on HN are getting out of hand. You can say it's not scalable, or that it doesn't have a future for A, B, C reasons, or any other number of valid complaints. But instead they've devolved to the most degenerate falsehoods that can be disproven with a single look at the long term chart.