Last night I loaded light room and found I only have 11 photos there (all imported last week). I use it regularly and have thousands of photos.
It sounds like you have opened the wrong catalog file. Try using the menu command File->Open Recent and select each catalog shown there to see if you can find the desired catalog.
I searched the hard drive for my back up catalogue files and they are missing.
This is not a good thing. Are you sure you are actually making backups? How do you know?
I plugged in my back up hard drive which I have not used for a while and it is blank.
This is not a Lightroom issue and so I won't comment.
I am wondering if I was to restore my computer to an earlier date if that would bring back my catalogue?
You need to find your catalog file, as I described above.
There are 2 items in the catalogue file. One is the catalogue file, created 7 days ago. The other is a folder with an file name extension of preview - when I open this it contains subfolders that are empty.
You need to search ALL of your hard disks, using your operating system's search feature, for files whose name contains .LRCAT