On the newer trailers the battery disconnect switch kills everything except the propane detector. While your fridge will run on gas, it needs some power from the battery to keep the "brains" working.
If you are sure you had the disconnect fully in the off position, you may have some problem with the switch or how the fridge was wired. Once you get the battery back in charge you might try to turn the swtich off and recheck things again. If the fridge stays on, try some of the interior lights and see if they work. You will find out quickly if it's a switch issue or fridge wiring.
'04 Classic 30' S.O.,'03 GMC Savana 2500,'14 Honda CTX 700