[upofadown]

Then you have lost that particular identity and would have to start over with a new one for that particular aspect of your online life. If you lose it and can get it back somehow then it wasn't really yours in the first place.

You can have as many passphrase protected backups of your identity in as many places as you like so in practice the more likely issue would be where someone else gets access to your private key. So that means some sort of revocation contingency.