From the pilot's description it sounds like a clean separation of the entire prop.
A blade failure would have been much worse.
Did I read somewhere sometime that excessive installation torque could result in failure of the bolts over time?
Anyway, kudos to the pilot for remaining calm, identifying a suitable forced landing site and bringing the plane in at proper speed and attitude.
Were it not for the ditch, this Piper would probably need nothing more than a new prop and an inspection of the gear.
That the pilot remained calm and called his wife after exiting the airplane is awesome.