Wow, I had no idea that there were so many missing Shadow episodes. I wonder if it's possible that some episodes were given more then one title (as in the Harry Lime series). IMO, The Shadow is more important in the formation of the Mercury then many Welles fans realize. Not just because of the fame and money it gave Welles, but also it's where he, Moorehead, Erskine Sanford, Paul Stewart, and Everett Sloane solidified their ensemble chemistry, playing the same characters week after week.
One of the articles in the new Welles interview book says that when the Mercury went on the road with their Ceasar production, Welles found that his fame as the Mercury's director was dwarfed by his fame as The Shadow. Of course, this was just before War of the Worlds.