Originally Posted by thenewkid64
...I am willing to bet the refer is the culprit here...
I will "second" that, but with a different scenario - chimney fire. On my Dometic, the exhaust from the pilot light travels up a metal tube about 1-1/2 inches in diameter, and about three feet tall. If the pilot light is adjusted too rich (yellow flame), soot (non-burned particles) will build up in this pipe. And, after a period of non-use, I would think you could also have spider webs or other debris. Once the refrigerator has been running on propane long enough, this soot can catch fire.
A propane leak is possible, but not my first suspect. Propane is heavier than air, so any leakage will stay close to the floor. Don't know about newer Airstreams, but on my '67, there is a grate on the floor to provide air to the refrigerator. The leaking propane would find this grate, and exit the interior.
Unless Columbo and I are able to interrogate Mr. Dummy, we may never know exactly what happened.