Actually that doesn't sound too surprising. Given the likely secrecy of working at apple, its likely you might not know what the guy working down the hall is working on. Maybe some manager went to take inventory once a month (or to have them destroyed after a prototype cycle) and found one missing.
Working on prototype in Apple must generate a lot of focus, from my point of view. I agree there are only few involved but they do work on it almost 24/7. We all know SJ and his approach to details/hard work at Infinite Loop.