I think the missing part is the rudder. It was located and recovered. Nothing sinister there. Th photos are revealing. I wish I knew enough to know what they show! Sure are clean breaks...
Crap, the pic got removed by the moderator (I really hate that, people shouldn't be so twitchy with the abuse button, or JR should change how a person gets pulled, I've lost some real useful stuff because of other things the person did), but on one of Tuesday's threads there was a great side by side of the tail getting pulled from the plane and a file photo of the plane working. You could really see that the part coming from the bay was the upper-forward third of the tail. Obviously the upper-rearward would be the rudder. But you could clearly see in the file photo that the lower A was a few feet above the fuselage, but only a few inches from the bottom of the recovered section. This actually gels well with the picks here since you can clearly see in the fuselage photos that it was not a clean break from the fuselage, but the bay piece looks like it came off clean.
I think what we've got is that the middle area (part between the A and fuselage) "disintigrated" (for lack of a better word). This would seem to reinforce the NTSB's current position that something caused the joining area to weaken, then when it hit WT the assembly couldn't take it any more, fell apart leaving the main tail intact but no longer part of the plane. It also really weakens the bomb/ sabatoge theory. That's a very long but short area to blow up, very difficult to do without damaging the rest of the tail, and there's no reason to put that much effort into a terrorist attack; and the pattern of failure is inconsistent with most plausible methods of sabatoge, which would focus on the bolts which are clearly still quite firmly in place.