Oh I fully agree - that's one of the assumptions I was making since trying to work out how much of a typical knight in plate was actually flammable sounds like too much modelling for me.
Or a ring/spell of fire resistance/immunity.
That said I believe that using treated hides or leather was popular for fire proofing things in siege situations.
Sorry, I took your 3am and 55mph comment literally and had you pegged at GMT+7, putting you somewhere around Thailand.
I would expect anybody living in a magical environment would well be aware of particular signature spells, let alone an experienced fighting man who's probably been on the receiving end a couple times already.
In D&D terms, I think overcoming your natural reflex would probably a Will save, but I believe fireball and other such spells are Reflex saves to represent you getting the hell out of the blast zone.