Seed phrases are bip-39. This is new and developing still and so backup is under construction for some wallets, as I understand. But to your point...you couldn't back up a token that has had been lost (lost phone). When your wallet falls into the river and washes our to sea, your cash money is gone. I'm not completely sure if this, but I think it's right. I think that's the whole point...you own the token (or not). Hope that helps. If you fins out I'm wrong please let me know!
Discussion
In minbits it has an off devive backup for if you lose your device. I assume that means the state data is backed up on nostr relays and you can recover with bip-39 seed?
I don't know how you can do offline transactions and prevent double spend. If you pay someone offline, but then restore your wallet from a backup before they come online and connect with the mint, wouldn't the money you gave them be invalid?
If you transact offline are you trusting the other person until you can connect to the mint?
#cashu #asknostr
You ask good questions, I don't know the answer and have been wondering myself. On the list of things to look up and figure out.