Found it on my machine using a an OS bases file search utility:
C:\Program Files\FileMaker\FileMaker Pro 11 Advanced\Extensions\Web Support\Resources\iwpres
I'm running FMS on OS X Lion Server which was why I couldn't see the iwp_home.html.
Within the wpc/ folder is an app called FM Web Publishing. I had to right click and "Show Package contents" which allowed me to do a search for the HTML file.