I am using an iMac with iOS 7.0.4. All of the photos were on iPhoto '11 after I updated to 9.4.3, and Aperture 3.4.5, but a few months ago they all disappeared from the iPhoto and Aperture libraries, Events, Photos and Faces sections. A few weeks later, I noticed a bunch of new folders on my external hard drive with the same title in a serial list of numbers, had somehow been created. Since I still had the pictures backed up on an external hard drive, I didn't worry about it too much at the time, but today I needed to find a picture from years ago and that brought up the need to fix the mess. In opening the 200 or so files that I have already opened, I noticed that they all listed in their details that they had been modified on 7/27/2013, from 12:07 am to 12:33 am (I guess it wasn't the 2 yr old's fault after all, because she would have been sleeping, sorry kiddo). The peculiar thing is that there is no rhyme or reason to the way the photos and videos were put in the folders. Some folders have only photos from a broad range of time, some have photos and videos, but none of them are sequential in time within the folder. When I transfer the photos and videos out of the folders, into the main overall picture folder, some of them are already in the main folder and some of them are not, meaning that I can't just take for granted that they are all copies, and delete all of the folders with that certain name.
Since I have now cleared my child of being the culprit for all of this mess, I'm thinking it must have been caused by a computer glitch or an update, as Terence suggested, especially considering the time of night when the changes took place. All that is listed in the software update section of my System Preferences area is an update to the AirPort Utility to version 6.3 on 7/26/23 at 12:23 pm. iPhoto had updadated to 9.4.3 on 4/27/13, but none of the files showed modifications on any date other than 7/27/13. Aperture had also updated to version 3.4.5, but it had updated days earlier on 7/11/13. Nothing had updated since 7/11/13 until AirPort Utility updated on 7/26/23, and nothing updated after that until 9/12/13.
