Amid all the cement and steel and bodies that fell from the sky in the World Trade Center collapse, there was art. Most of it was destroyed that September morning, but a few sculptures tumbled a quarter-mile before coming to uneasy rest in the fresh hot debris. They were Rodins. A bust from ”The Burghers of Calais,” its mask of dignity now dented. Two of the three anguished figures from ”The Three Shades,” broken almost beyond recognition. And, it appears, a cast of the artist’s most famous work, one inspired by Dante: ”The Thinker,” in endless contemplation of the human condition.