Missing Core Columns

At one point (before I moved to the mini-nuke camp), I counted up core columns in the north tower debris pile.

Almost certainly, there are hundreds of huge core columns "missing"-- perhaps even 90% of the expected columns are missing. The question is-- are the columns vaporized -- or is there some other explanation for where they went?

Other possible explanations:
1) many more columns are buried under the pile
2) the picture was taken 9/23/01 and many of these columns were taken away before then
3) upper core columns are smaller than the huge lower ones and are not clear in this photo.

None of these explanations are very satisfying as:
1) the core dropped last according to the videos, and core columns should have been on top
2) pictures from very shortly after 9/11 don't show hundreds of huge CORE columns in the north tower pile:

Also, these columns were massive and I would think that a crane lifting one would need to be closer in to the pile before attempting to lift them out
3) every WTC diagram I've seen has shown the core columns in the upper part of the towers as similar dimensions but with thinner steel

So-- WHAT HAPPENED TO ALL THE STEEL THAT SHOULD HAVE BEEN THERE??????