Did you try to do a search for .lrcat files on your machine and check if you find the one you were looking for?
In Lightroom 5, you can go under File menu> Open Recent> to get a list of the recent catalogs that you worked upon and check if it lists the required one.
Thank you for the reply Chetna.
Yes, I did try that but unfortunately, did not get the results I expected. There's nothing else missing or lost in my system. Would an overnight update wipe away files by accident? That makes no sense.
I keep getting prompts to upgrade to LR 6 CC which I don't really need, since what was upgraded is not that important to my current workflow and I don't want to get into a monthly expense on something I'd rather just buy upfront. *sigh*
Thank you again for the feedback Chetna. I appreciate it.
An overnight update cannot cause the catalogs to go missing or deleted.
Even upgrading also would not help in this case if you do not have your catalogs which were being worked upon.
Did you backup your catalogs on an external drive or anywhere else apart from your local hard drive from where they can be possibly recovered if possible?