How do you avoid losing that key?

As stated you can generate backup keys, but you can also associate more than one hardware token to your account. Which is what I do. I keep a separate yibikey in a lockbox off site as a break glass option.

They have a recovery sheet you can print. If you lose your key, you can use the recovery information on that piece of paper to regain access. You put the recovery information in a safe place.

That is also exactly why people like myself are so against passkeys, there are no offline recovery.