Does anyone have any idea where my photos have all gone? Or how to access them?
I did back them all up to "the cloud", but I have no idea how to access it.
Use your operating system's search feature to find the photos, search all hard disks for .JPG or .NEF or .CR2 or whatever the proper suffix is.
Lightroom doesn't ingest all of your images. They are in folders on your computer. They are in the folders that you chose when you imported the images to Lightroom. The Lightroom import process simply shows Lightroom where the images are located. Removing Lightroom from your computer will not remove the images.
I have found them, thank you very much.