to unhide a hidden folder, go to the first page of SE (swipe to the right). Scroll down to Tool Box. Here you'll find the Hidden Folder. Reverse the action and you'll see your folder again...

This is very old comment and sad to see no responses. I am a new user. I have used the feature to test hide a folder but can't seem to inside it. I did not use the '.' trick. I need that folder back. Please advise.