Sync and backups
Your collection is saved to your account, and a local backup is kept every week.
Sync is on for every account: your collection is saved to your account and restored on any device you sign in to. Settings → Sync shows when it last completed.
On top of that, the app keeps a weekly local backup on the phone, three at a time. Settings → Data → Restore backup puts one back, replacing the current collection with the one from that date; the app asks before doing so.
Your data is never locked in: Export collection (CSV) is free, always. See export your collection.