The catalog file has no thumbnails or accompanying photo's. There is a file ending with .Previews.lrdata that contains previews of the image files that have been imported into the Catalog. The Catalog File .lrcat (LRCAT) does not contain any image files it just records info about your image files and the work you have done with them in Lightroom. See the image capture. Have a look at the video tutorial on how the LR Catalog works at the link below.
I tried to watch the video. Actually went to every file with .lrcat and attempted to open. The one catalogue which has the exact amt of photos as before shows thumbnails with no photos. And, when I try to locate within the computer hard drive, no luck. I typically can find my way through these issues but clearly these photos are somewhere but no where to be seen.