Lightroom Classic CC: Photos Vanished from New Catalog

I created a new catalog yesterday, and imported a recent wedding I shot. Made some adjustments, flagged a bunch as normal, etc...I switched catalogs to work on some different photos, then came back to the new one and...all photos have vanished. 

I've used LR since 1.0 so I know what to look for...There shows the number '0' beside 'recent imports', the folder which the photos reside isn't even visible (should have nearly 4000 images), no previews for anything (why would there be if LR sees no photos in the catalog). The external drive where the photos live is green-lit in LR, and the photos show in Explorer though.

I open catalogs via the context menu in Windows, which shows recently accessed catalogs. The one I just created is indeed there, but it's like I never imported a thing. It's completely empty. I've never seen this in all my time using LR. Even the preview folder for this catalog is suspiciously small. 

I've searched my computer for a possible random duplicate of this catalog, but nothing comes up. What's happened here? I'm totally stumped! 

*update* - I've noticed a couple of files named 'Temporary Import Data' exist within the catalog folder despite the catalog / LR being closed. Could this be suspect? I didn't abruptly exit LR during an import or anything, so I'm not sure why these files would still exist...Thoughts?