by Julieanne Kost
To have Lightroom show you any missing files in your catalog, in the Library module select All Photographs in the Catalog panel. Then, select Library > Find All Missing Photos. The missing photos will be displayed in the grid and “Missing Photographs” will be added to the list in the Catalog panel (see below).
Note: if “Missing Photographs” is already listed in the Catalog panel (from a previous search), you should choose Library > Find All Missing Photos again so that Lightroom will run the search based on the current state of your images (otherwise Lightroom will use a cached result that might not be accurate).