Off-chain balance can be recovered after wallet gets uninstalled or even after phone gets lost because encrypted channel snapshots are saved to Olympus server as well as to local file on a phone.
Note that mnemonic phrase is used as an encryption key in both cases so you still need to have it saved somewhere in order to decrypt your channel backups.
BLW periodically saves encrypted channel snapshots to
/storage/BLW/mainnet/encrypted.channels.bkp file. Once (re)installed wallet checks if that file is present and then applies user provided mnemonic phrase as a decryption key. Once decrypted BLW puts obtained channels back in place.
Olympus recovery is used as a measure of last resort in case when local backup is not available and works as follows: once a fresh payment channel is created it gets encrypted and sent to Olympus server, this operation is carried out once per channel. Olympus backup can later be retrieved and used to reimburse your lost channel balance back to your on-chain wallet using a
data-loss-protection protocol. Olympus recovery should be initiated manually by tapping a button in a wallet settings page.
Please note that following conditions must be met for
data-loss-protection to work: