With that warning out of the way and the freezer test having roused my suspicions I pulled the case off and took the motherboard out. iFixit has a great guide here for that process.
|Time to cook!|
Now that you have your motherboard separated from the phone's chassis preheat your oven to 195 degrees Celsius or 390 Fahrenheit whichever is appropriate for your current locale setting. While your oven is heating take out some aluminum foil and crush it into a ball. Un-crumple it so that there is still a rough texture as shown. This is going to help limit the heat transmission to the underside of the motherboard which we don't want to reflow. Place the motherboard on the foil and press it down. At this point attempt to get the board laying as flat as possible. You don't want parts sliding down the board on an angle if you overcook. Place the foil and motherboard on an oven safe cooking surface, a ceramic casserole dish will do nicely so long as it has a flat bottom, I used the spill tray from a waffle iron. So pick whatever looks good to you.
Remove your motherboard and let it rest until completely cool. Inspect the board for any physical damage, if you've really messed it up be extremely careful with reconnecting the battery. Who knows what you might have shorted out.
Reassemble your phone following the guide from iFixit and give that puppy a charge. Power it up and hope for the best!