A Fix Too Late For Some
Hopefully you haven’t been using Adobe Lightroom on an iOS device like an iPad over the past few days, for if you had there is a chance your photos are all gone, permanently. A bug on a recent update, not the most recent which resolves this issue, but version 5.4 of the iOS software has had a rather unfortunate effect on customers. If you happened to make use of it over the weekend, and you notice pictures are missing then unfortunately they have suffered perma-death.
If you only access via a non-iOS device, or you were paranoid enough to back up your photos to another device, be it Apple or no, then those pictures are safe and can be synced back to your iOS device. The same goes for pictures synced to the iCloud, they will similarly be unaffected.
So before you start up a mobile Lightroom session triple check the version. If you are running 5.4 stop what you are doing and update to 5.4.1 immediately. That will partially ensure the safety of your photos, you should also back them up somewhere else to ensure this can’t happen to you. Adobe has apologized to their users, but as of yet they have offered no additional comments to users nor when asked by The Register.
The photo-nuking bug has apparently been fixed, and updating to the latest version of the iOS app will keep you from losing your stuff, if it hasn't been lost already.