This country is so uptight. I've been in many public restrooms where a woman will mistakenly walk in. She turns red, giggles and walks out when she realizes what she has done. The men usually just laugh too, no big deal, including those standing at the urinals "exposed". Reverse that scenario (man in woman's restroom) and the cops would be there and people would be hopping mad. Mistakes happen. I'm not saying this is comparable to what happened in this thread, but still, I think everyone is way too uptight about things. My wife takes our small boys in to the bathroom at times in order to keep her eyes on them if she doens't feel good about the place.
While I was in Thailand, the cleaning ladies would just walk in at random times to sweep or clean without any notification or knocks. There were no stall doors or anything. They didn't care who was doing what in there. Awkward, yes, but not the end of the world. Totally normal to them.
Now I'm not saying that having a 12 year old in a women's restroom is right, but not the end of the world by any means.