To me it sounds like what you're actually doing is overwriting your existing catalog with a new blank one.
To open an existing catalog you need to go (in LR) to File, Open Recent and then select the name of the file.
My only fear is that you've already over-written the existing File with the File, New, select existing File, Double click......chain of events.
File, New is to create a New catalog. If you select an already existing file then you'll just overwrite it.
If this is the case ou need to go back to your back-up catalogs, preferably the most recent one.
If you have a backup file stored somewhere you can resort to it. That way you wouldn't lose everything. But you wouldn't want to create a new catalog and give it the same name as the old one. A new catalog needs to be created in addition to the one that you have already.
Thank you Nick and Jim,
I went out to LR file, Opened Recent and saw 2 lrcat files.
I'm assuming then I can double click the first (at the bottom) and it should launch the catalog that has all my missing photo's in the Library.
Right now the Library is empty, although I have imported one folder I am currently working on. My photo's are still intact on my hard drive.