An iOS 15 bug appears to erase user’s saved photos, and there is no solution yet available.
iOS users have reported missing files following the run of iCloud backups.
According to a few days ago report, iCloud backups are deleting some photos taken by users off their phones. Based on Mac Reports, The issue is due to an interaction between the Messages app in iOS 15 and iCloud backup.
If the user saves pictures from a thread in Messages and then deletes the line, the photos saved will be automatically and quietly deleted when the next iCloud backup is run.
These are the reasons why images that appear safe within your photo library may often be removed automatically at a later time and not just that, but also at precisely the moment you’d like to be secure with the knowledge that you’ve just taken the time to backup them.
As per Mac Rumors, the issue is still present even with iOS 15.1 beta 2. This indicates that Apple isn’t yet able to fix the problem.
As long as the issue remains unsolved and the problem is fixed, I’d advise against the deletion of Messages threads that contain documents you would like to keep regardless of whether or not you’ve saved them in other locations on your devices. If you’ve already cut your Messages threads, make sure to create backups of any photos you have saved before your next backup to iCloud.