[exo762]

From what I've read in docs posted above, identity key is copied from S-Android to S-Desktop. If you lose S-Android, there are two possibilities.

1) Your keys are safe (device was encrypted and/or you've wiped it remotely, whatever). In such situation you could be able to transfer keys from S-Desktop to new mobile. AFAIK there is no such functionality yet (remember, its Beta).

2) Your keys are not safe. In such case no recovery is possible. Notify all contacts about the fact that they should "reset secure session", forgetting your Signal identity and establish new Signal identity.

Anyway, this is the only solution on market with secure chats and multi-device sync.