Well, no backups, the technical term for that is "a problem". I think from this point forward, you need to commit yourself to making regular automated backups of all of your photos and catalog file to different physical disks, no excuses.
Your photos are not stored in Lightroom. However, Lightroom does create "previews", this is what you are seeing, but these are usually smaller and low-quality compared to the originals. There are plug-ins that can extract the previews from Lightroom. One such plug-in is here robcole.com - PreviewExporter