I've been following a tutorial and I've been adding materials to an object I modelled. All was fine until I accidentally used one of the viewport shortcuts but I'd forgotten to turn on "emulate numpad" as I am on a laptop. I seem to have selected or entered a collection of objects to the exclusion of the rest of them. Most things are deselected in the view port and I can't see anything in viewport shading. I can re-enable them but I seem to be unable to select the objects now.
How can I return things back to normal ?
Really sorry if this is basic but I can't figure out how to get things visible again.
Thanks for any help
Here is a link to the file