Just heard the Mission Control replay:
CAPCOM "we read your tire pressure messages and copy your last"
CDR: "Uh, roger ..." [loss of comm occurs]
IMO, this wasn't an instantaneous event but rather happening over a short period of time. Seems to me that if it was a spacecraft attitude problem, the words would have been different. I'd say a tile problem jumps to the head of the speculation line. Occam's razor and all that.
I tend to agree with you. If the orbiter had been in an unusual attitude due to drag caused by tile loss, they'd know about it and be reacting to it.