I also found this after some searching:
http://www.justanswer.com/car/43hbi-...rost-went.html
My rear defrost hasn't worked for some time now. It's possible it could have just been the first part of the switch to fail, assuming it has its own circuit. When the problem happens again, I'm going to check the fuses mentioned on that site. If they don't have power, I'm going to replace the ignition switch.
From the webpage - "in the under hood fuse box fuses 46 ( HTR-AC IGN ) and 47 ( ERLS ) has no power on both sides with the ignition on , I took out the fuses to check both are good."
EDIT: Tested 46 and 47, as well as the sunroof fuse. All three had very low voltage at them. I have purchased a new ignition switch and will swap it out shortly.