If you have deleted photos from your Albums or Collections, you can still get them back from thrash bin or the "deleted" section of your cloud storage interface. However, If you have deleted them from the deleted section as well, They cannot be recovered.
PS: Deleted photos stays in the thrash bin for 60 days before getting wiped out automatically.
My photos have disappeared. How can I retrieve them please help I had so many photos and now they're all gone.
Did you perhaps use the free version of Lightroom and did you uninstall/reinstall it? The free version stores the photos locally, not in the cloud. And if you remove an app from iOS, all the app data will also be removed. The only way to get them back would be to restore the phone from a backup.