In my experience the military record keeping is far more detailed than the civil paperwork.
The same situation applied to the Siouxs.
In fact one Sioux was resurrected from it's crushed cabin and the form 700
which was found lying on the seat pan.
It is not uncommon for civil aircraft to change hands with only the current log books being available. In other words no long term history.
I have a feeling that commercial interests had a hand in this, with no one wanting to disturb the market place by dumping a lot of ex military aircraft
into it.
Certification issues in the differences between military and civil versions of the same aircraft probably do play a part.
A number of years ago Bell produced a number of 205A's using aluminium rivets (military specification) in an area where monel rivets were specified in the civil spec. They were fined $100,000 per aircraft (ouch!!!)
American ex military aircraft were affected by the breakout programm where the military owned the drawings and had parts manufactured by companies not approved by the design organisation.
I do not believe that anything similar happened to the Gazelle.