By your account, it wouldn't have mattered what material your building was constructed of. Once the fire was able to generate heat it became perpetual. If parts of the building could be saved, as it appears maybe were, they are unusable. Mine started sometime around midnight. House located about 125ft from the shop. A "thump" awoke me. When I raised my head and looked out the window I noticed the yard had an orange glow. I jumped up and looked out the kitchen window toward the shop. Flames shooting out the windows. Nothing anyone could do was going to change the outcome by then.
How were you able to diagnose the cause so well? In my case we never knew how it started. Dodge diesel pickup, two jeeps, two tractors, two ATVs and a building full of shop stuff. My only suspicious thing was the Dodge truck. All four doors were wide open? Either the heat built up so much it spontaneously exploded the interior and blew the doors open? Or the fire started in the truck and did so? Within a few minutes of thinking about it, we didn't care anymore. Damage was done.
My shop was a finished pole barn, OSB lined interior walls and ceiling. When planning a replacement I wanted something less fire prone. So I bought an all steel building from Vargus Purdun (sp?). We hired a new slab poured. Then constructed the building ourselves. It was 42x50x10. Metal panels on the interior walls and ceiling. Vaulted ceiling, which was nice.
I've since sold that property and now am in a 39x48x14, stud built, metal panel exterior, osb interior walls, metal panel ceiling, heated concrete. I got over the paranoia and built what best suited my needs with no regard to flammability in product choice.
With all that said, if any of my buildings were full of the flammables that were in my old shop and they caught on fire, they too would burn to the ground.
In a shop, your chances of defeating a fire are over in a very short time. For me, the best part of my fire was it's completeness. The Insurance Adjuster drove up to the shop. Got out of his truck introducing myself and shaking my hand. Turned toward the shop with his hands on his waist. "No question here, it's a total loss".