I always make a backup to a separate drive every time I quit LR. If you do have a backup, unzip the folder and move the .lrcat file to the Pictures folder (or wherever you prefer to keep your catalog) and double-click on the .lrcat file to launch.
Thank you for the reply.I have a question, if I append the backup catalog to the new one, will the entry's (collections, virtual copies, etc.) be duplicate, and do I have the options to chose which of the versions of the develop settings I like to keep?
The backup will contain everything from catalog on the date you made it.
I don't know what you mean by append.
But once you have it working you can import other catalogs into it to create a combined catalog, or even import individual folders as a catalog with all their corresponding develop settings and metadata.