I went ahead and ordered another flex cable on the chance that I either had two bad ones OR I shorted the two I had with the oils in my skin. I feel like there is a short in the cable, because of the aluminum foil experiment. It seems like it's completing a ground between the solder points on the sensor and the ipad frame itself, and then triggering the sensor. Since I've ordered another flex cable, I may remove the flex cable and try a soldering experiment
Department Q, you are right, the red box indicates the sensor itself. The black part under the first + Magnet is actually tape covering the silver part. I believe you encountered the same tape if you replaced the wifi antennae. The silver part seems to be what allows the power button, volume, etc to function. This silver part just plugs to the PCB board.
I have no idea if this could be an ipad3 part. I hadn't thought of that. I got mine from BestDealUSA on Amazon and they say it's for ipad 2, but who knows really?
If I get the nerve to try a soldering experiment I'll post the results here. I'll also let you know how the new flex cable works out.
As a side note, one thing I've run across while messing around with the digitizer and flex cable, is sometimes once everything is connected and back together the back light won't work. Holding down the power and home button until it restarts fixes this. I don't know if you've already come across that and figured it out, but it scared the crap out of me the first time. Just saving you the scare
-ash