I edit remotely for people who live in different countries. They set up smart previews- extract a LR catalogue, compress and send to me. I work on the smart previews, export as a catalogue and send back. I was about 900 images into editing smart previews in a catalogue. I had Lightroom set to creating backups every time I exited Lightroom. Opened up my catalogue the other day to finish the last remaining 200 photos. All of a sudden photos are missing . When clicking the exclamation mark I get the pop up box of could not be found because the original file could not be found. I can't click Locate, as I do not have the originals on my computer, they are on my clients computer. I do realize if the original files are moved or renamed LR thinks they are missing. I have asked my client if she touched her originals. She said she copied them to an external but left them where they were still. I find it unlikely that my smart previews would suddenly know that her originals are changed since I'm not working on a connected internet cloud based Lightroom. Why are these files missing? I have installed a script locator to extract missing scripts. It didn't help.