From looking at the Winnebago drawings, it would appear that the intake to the propane furnace (not the heat pump A/C unit located in the rear of the passenger side of the motorhome) is located underneath the dresser in the bedroom area (maybe five feet from rear of motorhome) on the passenger side of the motorhome. Typically, the furnace intake would then draw air from the bedroom through a vent/grate along the bottom on the dresser. (On my 2006 Journey 36G the intake vent is located out in the open space on the floor, so I can not put an area rug in that space.) If something has fallen out of the a dresser drawer and down on top of that furnace intake on the floor that is located underneath the drawer, then just about all the air flow would be blocked. It may be possible that someone left the clear plastic flooring protector in place as well. Pull all of the bottom drawers all the way out and see if anything is blocking furnace intake itself. Turn furnace on and if you are getting good air draw into furnace at the intake point, then something is wrong from the output side of furnace. If so, then you will need to go through the ducting piping and the vents that are on the floor. If those vents on the floor are covered with area carpets, then that will restrict heating air flow and heat circulation, or there could be some debris that is blocking the air flow through the vents. If you are getting good air flow into furnace and out through the floor ductwork, then the problem is probably within furnace itself.
Let us know what you find out, as doubt one of us will have a similar problem at some point as well.