A couple of links that may be useful, in relation to exploring the snapshots you do have:
- https://community.fly.io/t/region-deprecated-empty-postgresql-backups/25830
- https://community.fly.io/t/can-an-unmanaged-postgres-db-be-recovered-after-host-failure-even-if-the-data-retention-limit-has-passed/25898
If you dig into these techniques, e.g. via fly postgres create with a snapshot ID, perhaps you could post here how you get on. This is not my area of expertise, but a detailed account may catch the eye of someone who’s done it before, and they may weigh in.