Adobe representatives have acknowledged a critical fault in a recent update to its version of Lightroom for iOS. It follows multiple complaints from users that they have lost their photos, presets or both in the event these were not backed up beforehand. The company has released a subsequent update that advoids these issues; however, it will not be able to restore the data for affected customers.
https://www.notebookcheck.net/Lightroom-5-4-0-for-iOS-and-iPadOS-causes-the-irreversible-loss-of-photo-and-preset-data.489255.0.html