Oppo
Show Hidden Photos and Videos auf Oppo
On Oppo phones running ColorOS, hidden photos and videos are not stored in a visible album. They move into a protected space that only opens through a specific gesture, which is why many people think the files were deleted.
To bring them back, open the Gallery app and go to Photos. Then tap and hold the tab bar area (the row showing Photos, Albums, and Explore) and confirm with your device unlock method, such as your fingerprint, PIN, or pattern.
Once confirmed, the Hidden folder appears with every photo and video you previously marked as private. From there you can view, unhide, or move items back into a regular album.
When this does not work
If the tab bar gesture does nothing, check that you actually hid the files through the gallery and not through a third-party file manager, since those use separate storage locations.
Forgetting the unlock method itself is a bigger issue: ColorOS ties the hidden album to your device security, so a factory reset or a switch to a new unlock method can block access permanently unless you back up the files first.