Christian,
After reading your post a couple of times, I think this is the scenario that transpired based on the info you supplied. Seeing that the batteries and salesman switch were on, I also believe the Inverter was on but in "standby" because the coach was plugged into shore power. If you lost power at the cabin, then the inverter came back on line and started using up the house batteries. If the house batteries fall below 10.5 volts, the inverter/charger will not charge them once shore power is restored. Once you started the coach, the alternator gave the house batteries just enough of a surface charge for the inverter/charger to recognize them and start the bulk, absorb, and float sequence. If you had the generator set for auto start and you started it from the "remote panel" , once it realizes that the batteries are fully charged it understands it has no reason to be running so it shuts itself back off. Hope this helps, Give me a call at 520-309-1260 if you want to talk further.
Merry Christmas! Fred