There is a big difference between the cannon fuse that is often mislabeled 'det-cord' and the real thing. I can also see shock tube being called det-cord. Real det-cord is an actual explosive and is illegal, the other stuff just burns. I'll bet that the police just made a mistake about what they found. The military det cord looks almost the same as military fuse. I doubt someone would go to all the trouble of acquiring det-cord without getting the other things necessary to use it, or for that matter traditional explosives.