Other possibilities include entertainment gear, e.g. DVD, sound system, tv, satellite dome or receiver, some kind of led decor lighting, a tv amplifier system, maybe a USB charging port, etc. Just too many things that could have been installed and are designed to get power via a "wall wart" plugged to a 120v outlet.
Definitely request the electrical and plumbing schematics from Fleetwood/Rev customer service. They can email them directly to you.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC