Which version of Lightroom are you using?
I was using Lightroom and it crashed the entire OS. When I restarted Lightroom could not fine the catalog I was using. How does a catalog just disappear?
Lightroom cannot crash your OS.It must be a hardware driver that might have stopped working.
Have you tried searching for the catalog by its name on your OS?
Also check your Backups.
Newest version. I lost about a months worth of adjustments!
Did you backed up your Catalog ?
If so try opening them and see if your Edits are there.
The newest version updated through the creative cloud. I lost a months worth of edits.