Thanks very much, quick and easy solution.
Removing the folder @ Hard Drive/Users/<USER>/Library/Caches/Adobe InDesign/
worked for me and it restored the little box and pen icon to the layers window. i thought the only preferences were in library/indesign , but they are also under caches! grrr.....
However at that article you mention above, it says "please share your corrupted preferences" however the link is a 404 and no longer exists. would adobe still like my corrupted preferences? i backed them up.