This once happened to me, one off my hens vanished without leaving and predator traces. I know she had went broody. She returned 10 days later down near the dam. But after being locked up for a week, she went and sat on eggs again, but this ime I don't know where.(because i don't know where the nest is) A few days ago i found some craked eggs and a small nest in the garden, ihping tha it is another hickens, but i thought i saw millefleur feathers....But who knows, maybe she will return after20 days