You're 100% correct. According to the news reports at the time the transport was characterized as being a "mistake", i.e. human error. I don't know the intricacy of warhead arming etc., but another article on CNN talks about codes being handled insecurely: <a href="http://www.cnn.com/2008/US/07/24/missile.error/" rel="nofollow">http://www.cnn.com/2008/US/07/24/missile.error/</a>