Did this really happen?
I submit that we don’t know.
See #56.
I submit that we don’t know
I'm wondering if it isn't a convenient way to block further inspections. A sort-of the-dog-ate-my-homework thing, but more like "there was a horrible accident" "we're sorry, but the nuclear material is now forever buried". "drat the luck". "it was all for peaceable purposes, we were not trying to make a bomb", "so sorry, but no one can examine the materials now", etc...