The bottom line is every time there is even a remote possibility of your camper sitting unused in freezing temperatures you better have winterized your RV for that possibility. Doesn't matter if you use it every weekend all winter long.
At a minimum drain your tanks and lines. For me, all I have to do is open the drains and faucets. For others you might have to blow them out with air to get all the water out or even fill your system with anti-freeze. Also put AF in your drains elbows of your sinks and showers.
Steve