I recently shot some images tethered on a Nikon D800. I shot directly to the catalog thinking that made sense. Apparently it was a terrible idea. Now Lightroom won't let me edit my images because it "doesn't know where the original files are". Of course, the original files are ON Lightroom. I don't know how to fix this problem. Can anyone please help? I'm stressing.
Your images are not "on" Lightroom, or "in" Lightroom.
They will be exactly in the folder destination you chose in the tethering dialog.
If you do not remember where that was- start tethered capture again from the LR menu and you should see the last used destination.
If you can see the thumbnails in the library grid view, right-click on one image and select "Show in explorer/finder"
If your thumbnails show the [!] icon indicating they are missing, Perhaps you chose an external drive that is detached, or you have renamed, moved, deleted, the files with the OS.