The initial thought is that you opened a new or empty catalog. Check your recent catalogs at
menu /file/open recent/
Where were they stored? On an External drive or an internal drive?
Are there any thumbnails in the grid view of the library module? If not then you opened a new catalog. Go to the File menu item and select Open Recent and see what is listed. If you have more than one catalog listed click on each one to open them.
I have no idea what drive it's stored on. There are no thumbnails & I did select Recents & there is nothing. It's like everything has been erased!!
Use your operating system's search feature to search all of your hard disks for files whose name ends with .LRCAT (might be lower case). Double-click on each one found to open it in Lightroom, until you find the one which has imported your photos.
So you have no idea where, on what drive connected to your computer, you stored your image files?
You should have some knowledge of where you placed your images. They must be on a hard drive you have connected to your computer.
Use the Search feature in the File Manager for the OS you are using to search for .JPG or .(The Raw File Extension of the make of camera you are using). What turns up?