I was looking through Console and noticed AirportBaseStation.app was being reported missing, so I checked CoreServices, and compared it with a backup from a week ago (no updates so nothing should have been different, right?). However, when I looked at the item count, my backup had 108 files, whereas my current had 98, among those missing files were AddPrinter.app and AppleScriptUtility.app. 
I copied them all back, but still, could anyone explain this?
I copied them all back, but still, could anyone explain this?