I also have a 32QB and found the floor under the slide soaking wet after taking it out of storage a week after we spent a weekend in it. It took a lot to dry everything up and thankfully the water had been in there only for 1 week.
I've looked everywhere for the source and have concluded that it's condensate water from the air conditioner that pools on top of the slide. The gutter on the slide-side of the 32QB is too small for the volume of condensate and it overflows onto the roof of the slide out. I've gotten into the habit of checking this area before retracting the slide - even bringing a broom with me to push the water off.
My next step is to put a piece of weather stripping on the roof to guide the condensate stream towards the gutter further to the rear of the trailer. My hope is that this will prevent the gutter from filling up and overflowing onto the slide.
2010 Zinger 32QB
2013 F-150 FX2 Ecoboost