Are there exclamation points on each photo (at the top right of the rectangle surrounding the thumbnail)?
Yes and forgive my tardiness in responding. I clicked on the ! and it told me the original had been moved. I suspect they are desktop photos that I imported and then deleted but really not sure. It took me to a search dialog box but not sure what to do as lots of folders, etc.
IF there are exclamation point icons on the photos, or question mark icons on the folders, you have to point Lightroom to the actual photo file or folder in whatever location it has been moved to.
All of the details are here: Adobe Lightroom - Find moved or missing files and folders
If the photos have been deleted, then you can restore them from your backups. If you don't have backups, then there is no way to recover the photos. You might as well delete the thumbnail from Lightroom.
If you are importing photos from your desktop (not your desktop computer, but the desktop screen), then I will state that this is a poor practice and ought to stop immediately. Put the photos in some specific folder and import them from there using the ADD option, or better yet let Lightroom choose default folder names (which is the capture date of the photos) when importing from a camera card using the COPY option.