Bull flops. Everything I know about fires, acid etching, steel, copper sulphate, pyrites and thermite (and i am sure, from the quality of arguemnets you offer regarding subjects which involve these things, that I know a great deal more than do you) tells me that the steel was just buried in a hot, wet environment with a lot of acid fumes and some copper. Can you prove that it was not? Can you prove that there is a form of thermite that leaves that sort of marks? It would surprise the bejeebus out of me if you could, because it violates every bit of the science that applies.
What UL report? Link it, and it had better be good if you want your credibility back.
And if that whacktard Kevin Ryan's name is in the link you provide, you get five of these: