That is so funny. I had a similar experience two weeks ago on our Milli cruise.
We were upgraded to a cabin with a balcony half way thru the cruise. Well, this cabin was totally reversed from the cabin we previously had. I, too, always leave the light on in the bathroom to find my way in the middle of the night.
So, the first night we had the new room, I woke up to go to the bathroom and headed for the "light". Next thing I know, I find myself standing in front of the sliding glass doors trying to figure out where the bathroom is. Luckily, my hubby and I were the only ones to witness my confusion.