You should be able to carefully pull plastic trim panel off the side and see the tube on the passenger side. You can drop the tray (there's one philips head screw that holds it on and then just pop it off, you can let it hang; no need to bother unplugging the modules) under the glovebox if you are having trouble getting it out/back in.
But that will let you know if it's connected to the HVAC box, you can pull back the carpet a little after taking the tray under the glovebox out and see if there's any holes or such on it's way out of the body.