(petapixel.com)
Yesterday afternoon, at 4:30pm Eastern Time, Adobe officially confirmed the issue, explaining that customers who updated to Lightroom 5.4 on iPhone and iPad “may be missing photos and presets,” that those photos and presets are “not recoverable,” and that they “sincerely apologize” to users who have been affected by the issue. Version 5.4.1 has already been released, fixing the issue, but it can do nothing about the lost data.
This is also a great reminder for photographers that you should always back up your images, in multiple places, so you’re never subject to a single point of failure. Mistakes like this happen, even at some of the world’s largest companies (see: canon.image).
THIS is why you need to have physical backups of your work/images/etc. like getting a external hard drive.
Latest update to Lightroom for iOS inadvertently wiped users' photos and presets not synced to the cloud; Adobe says there is no way to get them back