Macbook Pro with OS X Yosemite. For no reason at all suddenly all the photos and videos in the folders on my desktop have disappeared just leaving empty folders. I've also got a folder called Saved Music, all the music files have disappeared too. Some PDF files within folders have gone also. I have a few photos not in folders on my desktop, but they are still there. I've tried searching in Finder but they are not there. Anybody any idea what's occurred ? I've done nothing to my Macbook except switch it on. !!!