I did a image search and sure enough your power converter panel is below the fridge. I doubt if the furnace is behind that but, I could be wrong. I couldn't find a good images of the left outside of the camper but, it looks like there might be some vents below a big picture window toward the front of the camper. Do you have a picture window there and could the furnace be mounted under that somewhere?
Also, where are your outlet ducks? You know there must be round holes mounted inside the camper near the floosomewherere for the heat to come out. If you could find one of them maybe you could follow the tube thaattach'ses to the back side of of one of them back to the furnace.