I am aware that this problem crops up repeatedly (although rarely), and Adobe seems to claim that they can't find it. See message 27 by Julie Kmoch in this thread: https://forums.adobe.com/message/5230435#5230435
You may want to contact Julie Kmoch directly via private message here on this forum, and also cite these threads
In the meantime, you need to try the following steps in sequence:
- Check the trash/recycle bin for these photos
- Restore these photos from backups (you do have backups of all your photos, don't you?)
- Download and install and run an "undelete utility" program which may be able to recover the deleted photos. If you are going to do this, do not perform any other tasks on your computer, except to find, download, install and run this program (if possible, download and install it to a drive that did NOT contain the photos)
- Recover the thumbnails from Lightroom's cache via the plug-in http://robcole.com/Rob/ProductsAndServices/PreviewExporterLrPlugin/
Thank You! Unfortunately, I have been putting off buying an external hard drive, thinking that the backups on the computer would save everything, (extremely naive and feeling pretty stupid, you can bet that I will buy one and back everything up immediately). Do you have a recommendation for an undelete program?
Sorry, I haven't used an undelete program in about 10 years. There are free ones available for Windows; I would guess the same is true for Mac.
Go to your favorite search engine, type in
undelete utility free