Don’t panic! It is not unusual to hear reports of some or all photos seemingly going missing after a new version of Lightroom Classic comes out that requires the upgrade of a copy of your catalog. The release of Lightroom Classic 13.3 required a catalog upgrade as part of the process of using this new version of the software. When this happens, Lightroom Classic creates a copy of (what it thinks is) your working catalog, and then upgrades that copy to work in the new version, then opens with that upgraded copy. If Lightroom Classic opens and all seems exactly the same as when you last quit the program, then you are good to go, and move on using the new...