I had the same thing happen in my 2013 micro-lite 19fd dismissed it as condensation till one night I dropped a remote off the nightstand under the bed. I had my girlfriend flip me up behind the bed to retrieve the remote the next morning only to find not only the remote, but rays of sunshine from between the floor and the front wall. I ended up tearing out the bed, and re fastening the bottom of the wall and caulking the whole thing shut. Haven't had a wet pillow since.
2013 Flagstaff Micro Lite 19FD
2001 Chevrolet Silverado 1500 Ext. Cab 5.3L