I figured it out! I got into one of our base SR5's with cloth and turned on the rear window/outside mirror defroster
waited a couple minutes and felt the outside mirror, it was hot. So I felt under the front wipers and it was hot! The rear window/outside mirror defroster button also turns on the windshield wiper de-icer! The 2011 Sienna has this same configuration
If you have an SR5 without a de-icer grid (physical lines showing) and no button as seen in the 4Runner manual
don't worry you still have a de-icer, it's standard on all 4Runner's. There are little holes in the black area of your windshield right where your wipers begin and end. The 2011 Sienna also has no physical grid but multiple little holes in that area. Maybe this is a new way Toyota is doing their windshield de-icer.