The RV furnaces I'm familiar have either been the type that delivers all heat from single vent located right on the furnace (small TT), or a ducted one that delivers the heated air from
floor grates in a couple different locations in the camper (larger TT). So they have been either/or, not a combination of a vent on the furnace plus other ducted vents. Your TT seems relatively large, so it doesn't seem likely to me that it would use the furnace for a smaller TT interior space that only blows from a vent on the furnace itself. I would suggest looking around on the floor for heating registers and confirm if heat is coming from those. I apologize if this is what you are referring to in your OP, but it wasn't clear to me.
If there are vents in the ceiling, those are for the air conditioner and not the furnace. Air will not come out of those while heating unless you are using a heat pump feature and have a setting turned on via the thermostat to do so.
EDIT: I tried googling your toy hauler and didn't really find reference to a propane furnace, so maybe it doesn't have one? I see reference to an electric fireplace and this brochure says "5 kBtu heater" which is quite small.
https://library.rvusa.com/brochure/2...an-Lantern.pdf
This video walk through just breezes over the fireplace with no explanation. Although I see what looks like a vent for a smaller size furnace under the fridge at 1:29 into video. If that's the case, that is the only place where heated air will come out. Looks like one of
these.I see what look like an A/C duct in the bathroom but he doesn't offer any explanation.