Please launch the Lightroom while holding down the Alt / Opt key and it will show you all the recently used catalog files.
Otherwise the default location for Lightroom catalog is the Picture folder, you can check that folder Or check the Catalog backup folder
Thank you for the prompt reply! Unfortunately no back up. I am currently re importing the images, probably doomed to have to reorganize everything including all lost keywords, image manipulations, ratings, etc! Amazing that the catalog data just vanished. I will try the alt/opt option later this evening, currently I am re importing several hundred images. I have noticed that the catalog title does not appear at the top of the screen as it has in the past? Your attempt to help me is most appreciated.
Here is a screen shot of what is in the picture/lightroom folder:
I have a Mac...no alt key..
I did find back ups of my Mac here is a screen shot, but I don't think the date is in the backups either!
Alt (Win) = Option (Mac)