Hello, is the battery disconnect for the coach or chassis battery ?
Should be in the ground cable , if it's a coach batt disconnect. Look between the negative batt post and the frame.
Most larger coaches don't have spares, jacks or wrenches, because of the weights/dangers involved in changing a tire on the heavy units , previous owner could have set up the coach with the spare , to have it along, so they didn't need to find one, just need someone to change it. Speeds up the responce time for outfits like Coachnet, to get you help, if they don't need to find a spare before they dispatch someone to change it.