The other party would very likely close the channel forcefully after some time. It would be possible because channel participants constantly sign new commitment transactions which can be used to settle the balance on-chain once a certain timelock has passed.

Unfortunately, in this case, the other party could attempt to cheat by broadcasting some old commitment transaction. Normally, you would be able to revoke it and publish a penalty transaction. A watchtower could also do that, but it would have had to be set up beforehand.

However, not all participants of the network have malicious intentions. If the channel was closed using the latest commitment transaction, you would get all of your coins back to your on-chain wallet which you should be able to recover using your seed.

I am not sure how mobile wallets behave, but LND generates a backup file which lets you close your channels thanks to data-loss protection (note that in this case your peers have to cooperate with you). C-lightning users can use a backup plugin which makes a copy of the whole channel database. If you have such a copy, you can easily recover your node without having to close any channels.