Which Lightroom? Lightroom Classic or Lightroom? If you are working in Lightroom Classic are you on a Mac? Have you made backups of the hard drive with Time Machine or other service? If your only originals existed on the hard drive that was lost do you mean the drive is damaged or that the drive is not in your possession? If you have the drive have you tried any data recovery software to access the data on the drive? Please provide as much information as you can.
Are you saying that somehow, all of your originals photo files were deleted? If you have backups, then just copy them to the original locations. If you don't have backups, then why not?
The images you see in the catalog are small sized thumbnails, lower resolution than the originals (and if the originals were raw, then all you will get is JPGs). This plugin will get the thumbnails for you.