When you delete a photo from the upload page, it isn't actually deleted, it just doesn't show on the page, It can still be viewed via the ID. It's especially a problem because the admin photos page (which normally can fully delete photos) can't delete them once the uploader has "deleted" them, meaning the image is just stuck there, existing by ID, only viewable by people who know it or come across it.
The solution would be to either make the photos not disappear from the admin page, or actually delete the photo when deleted from the upload page.