What Chassis do you have? Don't go by the "Coach Year" rather get the Date of Manufacture from the chassis builder's label in the door jamb.
Have you been able to drive this coach? Gotta be a Chassis Battery somewhere, unless your Deep Cycle is installed as Chassis...
I looked for "Battery Switch" in the Owner's Manual and only found it mentioned in that list of things powered by House/Coach Battery. No reference to where it was or how it worked/when to use it.
Could you post pictures of the underhood area?
Sometimes, House Battery is concealed in places like under a step well. But at least in Class C, I've never heard of Chassis Battery NOT under the hood. And if it's a Ford, Chassis Battery is usually passenger side.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB