As you know there should be four folder views (big icons, small icons, list, and details). I just cannot get 'details' to show up anymore. They are invisible. I know that they are there (somewhere) because the number of objects is displayed at the foot of the window.

By the way there are no hidden folders set.

It sounds like the column headings across the top have been moved all the way over to the left thus hiding the entries.  Try putting your cursor up there and see if it shows a double bar with arrows on each side.  If so, you should be able to drag it to the right thus showing that column.  Do this for each column until all of them are showing.

There was a bar atop the window which was not present with the other three folder views. There were no arrows but I managed to manouveur the headings to the right and the details came into view. Thank you for your excellent diagnosis!