The search would certainly go faster if a dozen front end loaders were used. The results might be a bit messier, though. Dynamite could also be used to pulverize the rubble to make it easier to sift.
It is an impossible job....Finding someone who was on the lower floors is impossible...you have twelve floors on top of the first floor...it is done so they can say they tried...just Lady Luck at this point...moving concrete with rebar is hard to do...every thing is all twisted...rebar has to cut ...