Hope the picture I posted in post 275 is clear for you.
What can be said from this picture is that on the norwegian crash picture neither the head of the pin, with two flat cuts nor the two safety pins are visible.
The question then is why ?
Gone as a result of the MGB explosion : possible
Gone as a result of a maintenance flaw : possible
Just one thing: the pin are tight fit, with no play in the vertical (lift) axis, they are not rotating parts, thus, I think that a lack of safety pin would not be noticed by a vibration monitoring system.