Yow! Sounds like you were the victim of a bad design. From what you posted, I can't see how you could have been more careful.
My 17' trailer does not have the rigid panel you speak of. It uses a heavy fabric panel between the ceiling and the edge of the sink counter. It is permanently fastened at both the top and bottom and it simply folds when the top is lowered.
At the entry point to the toilet area, there is a swinging lower door attached to the lower half and then there is a sliding curtain (again, fairly heavy cloth) that closes the upper half to afford privacy. We've never found this setup to be wanting, even with grandchildren aboard.
Possibly, you could modify your trailer to have something similar? I could post pictures if you are having trouble visualizing my setup.
Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH, Progressive Dynamics Converter, Fan-Tastic Fan
2014 F150 Platinum 4x4 3.5L EcoBoost SCrew