This is the second time this has happened this summer. I did find this link with a similar problem.
I turn on the furnace and hours later, while sleeping, I wake up to find it is not running. I turn it off and then on and it stays running and cycles. Hours later I find it has stopped again. It got down to 36 degrees outside and 49 degrees inside. I did not inspect inside of the vents, but both inside vents and the outside vent had air coming out of them. I had the fan on low but I do not think there is a difference between low and high when using the heat. I am running off of battery only and it was a little low at 12.2 when I got up for the day. The refrigerator worked fine, if it was a propane supply problem I would expect the "check" light would be illuminated on the refrigerator. I have two propane tanks that are supposed to switch if one goes empty. The tank it was running on was pretty low. By looking at the frost on the bottle I am thinking it only had about three inches left. I only have one more night planned before I bring the trailer home for the winter. It will be just as cold then. I am planning on doing a quick vent inspection and switching to the full bottle. Any other ideas would be appreciated.