Though I have tried to move folders and files only with Lightroom, I note that a good number of my images shown in thumbnails in Library cannot be opened because Lightroom 5 cannot find the files. I assume I have moved files among drives accidentally without Lightroom's knowledge. I also note that I can control click and try to find individual files. Is there any way to do this find process for entire folders or drives? Can I import files from a drive (which is the original source of the lost files) in mass and run them through the import function on Lightroom and return them directly to the file from which they were imported? Would this create a new thumbnail in Library but duplicate the files in the affected folder and drive?
Lightroom isn't going to allow you to import images a second time. In the left-hand panel of the library module you can Ctrl-click on a folder and choose to update the folder location or find the missing folder. Have you tried that?
Jim, thank you for your answer. I have used the approach you enumerated but there still are a number of lost pictures. Perhaps I have not gone done to the lower folders which I will try.