Jeremy, that theory of the Grand Staircase floating out at once and intact has been mooted befor. While I won't go so far as to say "Utterly and non-debatably impossible" I will point out that there are serious problems with that theory. Not the least of which is that the opening over the Grand Staircase is not large enough for the whole column to just neatly float out.
Even if it was, there is the matter of the violent forces at work vis a vis hydrodynamic flow over and through the structure which would virtually gaurantee that nothing would neatly float out. I'm in agreement with Parks Stephenson's theory that as the ship went down, this area of the ship in effect became the world's largest Cuisineart Blender and that these same forces tore it to pieces. I have a sneaking hunch that the chunks are still there, scattered in and around the wreck, and buried in sediment.
Yes, I could be mistaken, but in this case, I wouldn't bet money on it.