Any soldier in the Army that loses a sensitive item or leaves it properly unsecured is punished severely with Article 15's to Court Martial and loss of rank depending on the item lost. These sensitive items could be weapons, night vision devices, radios, code books, maps, and the list goes on and on. These individuals are not even drinking but are punished because of the potential security ramifications it could lead to if one of these devices fell into the wrong hands. Apple is treating this prototype in the same manner as the Army does it sensitive items...thus is my opinion that the Engineer is just as responsible and negligent as a soldier who loses a same type of item as far as Apple is touting it being a secret device.
You are the one conflating a missing phone to a piece of missing material is deemed secret by the USG. Apple is treating this like any tech company would treat a prerelease device that has gone missing.
We have no idea what the ramifications are between Apple and its employees on such matters.