I did a lot of work on a particular day recently. I then appear to have inadvertently lost all the original files from my hard drive - I suspect when I was trying to remove one file from the disk via LR, I inadvertently had all the files from that session.highlighted I was able to restore the files to their original positions on my hard drive from the recycle bin, and then re-upload them to Lightroom Classic CC. When I subsequently opened the photos in LR, they appeared as the end-product of the work I had done on the original photos, but I was unable to open any history of what I had worked on. All that appeared in the history panel was "imported" (with the new date and time). Any suggestions as to how to recover the history of the work I did in LR?
You will only be able to restore History from a Backup Catalog that contained the History. ie. the Catalog Backup was created after all the Development work.
If no backup of the catalog was made, then your develop history is lost. My sympathies.
Importing a second time NEVER restores History. Perhaps you were automatically saving metadata to xmp which has allowed the appearance of "end-product work" - Some small consolation.
If all this happened just after doing the edits, IE Before LR or you did a catalog backup that contained those edits, then all of them are gone. Once you remove images from the catalog, whether or not you Deleted them from disk, LR erase all the edits done on those removed/deleted images.
So you will need to start over.