if you loose your phone you loose also the 20 bucks of ecash, I frankly dont see this a problem. 
Thinking how recovery could work, maybe on every payment the wallet could do a self-payment-locked-to-your-id and upload it to service provider, like zeus manage backup of channel data. I think is more or less how it is intended to work a pay-to-npub with ecash stored in relays. 
Ecash will change a lot and we will see how it will push the limit of magic internet money.