I've dragged an email attachment to my desktop. Its name began with a dot so Mac sees it as a 'hidden file' and the icon can't be seen on the desktop. So I did a search with the 'kind' option set to 'visibility: invisible'. But it doesn't show any hidden files. No file that starts with a dot. Terminal does show it when I use ls -a. So why doesn't it show when I do a 'hidden file' search?