Just listened to the interview and to me this sounds like a right cock up from start to finish!
Its all well and good to use the "What if a child had found it" HH but that did not happen and by the sound of it could not have happened!
Someone I know was called to a neighbours house to help after the old chap had a suspected heart attack. He was astonished to see firearms from the second world war in the house. I believe they were all handed in for destruction and the case was not taken to court.
Surely this is what should have happened here? Just a little bit of commom sense and a word from his commanding officer should have done the trick!