What it means
Locked Folder keeps selected photos out of the normal Photos grid and restricts access using the device screen lock or Google Account password. Backup for Locked Folder is a separate choice. Unbacked items remain only on the device; uninstalling Photos, clearing app data, resetting, damage or loss can destroy them. Backed-up items can become available on other signed-in devices, which improves resilience but changes where the data lives.
A real-world example
A traveler moves scans into Locked Folder, assumes ordinary photo backup covers them, then resets the phone. The scans were unbacked and are no longer available. A separate folder-backup check before reset would have revealed the gap.
What to do
Inspect the Back up Locked Folder switch, verify the correct account and confirm important items from another trusted device before replacement. Keep a separate secure copy of irreplaceable records.
The distinction that matters
Privacy from the main gallery is not secrecy from a person who knows the device screen lock. Cloud backup is not the same as an offline copy. Choose the tradeoff deliberately for each sensitive item. If you move a photo there, related edits, duplicates and copies in messaging apps may remain outside. Inspect them after confirming the Locked Folder item is intact. A reset should be the final step only after the backup was checked from another device.
Google Locked Folder behavior
