We are sorry about the experience with Lightroom Classic.
Would you mind confirming if you had the catalog saved on your computers internal storage or on an external drive? You can go to the "File" menu in Lightroom Classic, then Open Recent and check if you see your working catalog there.
Once you find your .lrcat files check the dates to see when you've last opened the file and look for the date that you think it should be.
You may want to change your preferences so that Lightroom will give the list for you to choose from when opening if you want to keep old catalogs. In your Preferences > General tab > change Load Most Recent Catalog to - Prompt me when opening. This will show catalogs that it finds on your computer and if you have catalogs on an external and that EHD is connected and running.