Susan,
We live about 12 miles from Lake Zurich. Please contact me if I can help in any way.
I wish I had thought of this sooner. Lake Zurich has a very large and active running club.
http://www.alpinerunners.com/
By contacting them you could enlist a small army of individuals regularly afoot in the area. Runners tend to seek remote, low-traffic locations and trails, perhaps locations a scared dog might seek seclusion. Loose dogs and runners regularly encounter one another.
Back when I was an avid runner, this club used to host an annual Thanksgiving morning run (both a social event and a pre-feast workout) that had a large turnout. This might be a good opportunity to make a face-to-face request for help from this club.
Again, I'd be more than happy to help with any efforts to find your friend's dog.
Jim