Firstly, its a terrible explosive for actual military use. If you can pull strings on this scale, you can obtain something more practical.
If you are planning terrorist attacks, you don't need a mountain of the stuff, because there is no plausible scenario for using it in such quantities.
Secondly, if they had a plan to use it, they would have moved it somewhere sensible, and have it guarded / stored properly, they would make sure its not lost in a terrible accident.
