That's fine, as long as the warheads could not be detonated it does not matter where they go.
The point is that you can arm a British nuke in 98 with a bicycle lock key and no tamper-proof mechanism was there. So if you got a warhead detonation was easy. In the US having a warhead is pointless, you need the codes or the bomb is worthless.
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: http://www.cnn.com/2008/US/07/24/missile.error/
The point is that you can arm a British nuke in 98 with a bicycle lock key and no tamper-proof mechanism was there. So if you got a warhead detonation was easy. In the US having a warhead is pointless, you need the codes or the bomb is worthless.