Exceptional claims require exceptional evidence. In an era when transportation was more expensive than manual labor, why would they go to this much trouble for a building? In cutting down the building parts to pass through so many truss bridges, you'd have hardly more than a stack of lumber. There was plenty of new lumber to start with and quite a few handly carpenters in this day and age. Add to it this would be a rather notable activity in the busy downtown of Denver, and it escaped mention in all the newspapers, and in the paperwork of the railroad?
Best Regards,
-Nick