First, realize I'm not an expert, (Like that's not obvious) but you asked for input.
Your friend's scenario rings so true, it has to be very close to the root cause.
I would just add one thing that has been stuck in my mind since Saturday morning.
On Columbia's first flight in 1981, they lost a few tiles from the frontal area of the port side OMS pod. I remember Young and Crippen peering through the flight deck rear windows, and Crippen was looking a little uneasy. At the time, (being this was the first Shuttle launch) there was a palpable if subdued apprehension as to whether Columbia would survive its very first reentry. (This was mostly hype from the media, but I was a little scared)
There was also some discussion from some folks familiar with the Tile technology, referring to phenomena called 'zippering'. The idea being that under the right circumstances, a loss of several tiles might lead to a runaway effect, which would denude the Orbiter's skin, in a sort of domino-jig saw pattern.
In addition to the left gear door damage, and conflagration, perhaps 'zippering' could explain some of the anomalous heating, maybe even above the left wing.