Recover hidden videos on iPhone

The Hidden Album is available in the Utilities section near the bottom of the Photos window:

(Unless it was moved with "Customize." In that case, look in the Customize menu.)

In Hidden, when you select a picture, tap the (•••) More button to get this menu:

and choose "Unhide."

Then the picture will disappear from the Hidden album, and it will reappear wherever it was before-- in the Library, for instance.

Does this work for you?

Hidden videos don't need recovering as they are in the Hidden Album of the Photos app and access with FaceID/Passcode.

If you deleted a video, they can be recovered from the Deleted album for 30 days. After 30 days or if they are deleted from that album, then they are no longer recoverable.