Yes/no riddles on the topic Japanese

A little girl was warned by her parents never to open the cellar door. If she did, she would see things that they did not want her to see. One day, while her parents were out, they accidentally left the cellar door unlocked. The girl opened the cellar door. What did she see?

Today, I was on the train again when a woman appeared before me. I didn’t even remember her face. It’s so sad. Explain why the narrator feels sad.