That all makes sense, and it is plausible that Emmet would have been in the area to build Iroquois. From the article, it sounds like Iroquois was definitely completed and put into service at some point. If it no longer exists, it was like built over by houses in the 1950s like other suburban courses in Upstate New York.
Also, Battle Island is still in existence. It is south of Oswego near Fulton, New York (the home base of this new history website, I believe). From the air, it appears the course has been stripped of bunkers and overgrown by trees. However, it looks like some cool land features still remain.