Importing pictures into Lightroom Classic from external drive for which the catalogue lost

If you DON'T write changes to XMP then it is absolutely critical that you maintain backups of your catalog because that is the only place that your changes to your images are stored. In that case the images don't have any sidecar files, there is no additional record of the adjustments made, and the catalog is the only record of the changes you have made. I don't write changes to XMP, and have only had to rely on a backup catalog once in the last 10 years. I know, some will argue that I'm reckless. But I'm comfortable with the way it has worked.

Sort answer, as stated above, is no.

Use the option to Auto write changes to XMP. That will at least save all the actual edits to a sidecar XMP file that then can be read if something like this happens again.

Also you can chose where the LR Classic Catalog Backups are stored when the backup dialog comes up. I suggest you select an External drive to store the backup on. Also make a second copy of all your images and the catalog backup on another, second, third,whatever number, external drive.

Please note that no actual images are in the LR catalog. So if you don't have a backup of the actual image files and the external drive that you store them on fails you will lose all your images. Back Up the images and then Back Up the Back Up.

Redundancy is the key to not losing your data.

If you don't have the old catalog, and you don't have backups, and you didn't have Lightroom write the metadata to XMP (this is an option in Lightroom you can turn on), then your edits are gone. Next time, you need to make regular and automated backups of your catalog file and photos, to a different drive than the originals.