WebAuthn private keys don't exist at all outside of the physical token. So there's nothing to manage. If you rely on WebAuthn as an essential authentication step you'd have two or more tokens registered and treat those the same way you would house keys.

When you lose a house key it's pretty manageable to get a few locks changed, but it can be rather overwhelming to remember all the dozens of websites that have your auth details, and update them.

Good news. Like a house key, the FIDO keys are basically anonymous. So, as long as you didn't e.g. leave it with your wallet on a bus, or write on it with non-erasable marker "[email protected]" losing the key is not that scary.

In fact, unlike a house key, the Security Key works fine for its new owner, they can register it to sign into their Facebook, or whatever, that will work fine. Facebook will have no idea it's your key, now it's their key.

If they know you're [email protected] on Facebook then that's a problem, yes, as obviously they can sign in as you, but if it's so hard for you to remember what you signed up to, seems like it'll be pretty hard for a hypothetical finder to figure out too... "Hmm, I wonder if this random stranger was into Diaper Porn and Antique furniture?"

AKA "wallet"