The AT shell, wouldn't go bang in a million years unless it goes through a very specific series of actions to arm it...so everyone getting excited about it is a bit Daily Mail. Every weapon goes througha vast amount of Ordnance Board tests to ensure they are safe to handle...including dropping it from height onto all sorts of surfaces to ensure it doesnt go bang,...it also has to endure heat and flame tests, so panic over return and stow all outrage.
Having said that, it would be a cnuts trick to open and investigate in the way described... sounds more like an AB gunners trick to me.