I have no idea is there is a lock on our Class C bathroom door. There may be. There is a lock on the shower door, which is weird, I would never shower with the door closed. Our bathroom is in the middle of the RV and the shower door opens to the front and clicks in place, the toilet door opens to the back. This makes a larger space when showering and allows the bathroom fan to get the steam from the shower out.
We spent last weekend in a friend's Trailer, I have no idea if there was a lock on that door either.