I was looking through a file my OWC Mercury Elite Pro 2.5" external HDD that contains all of my music and I noticed that some folders had been deleted, some folders had been added and some files had been moved around or renamed. I did none of this and I don't know how this happened. Could this be a symptom of a bigger problem or did something simple go wrong. I'm running Yosemite 10.10.5 on an early 2011 MacBook Pro. Thanks everyone.