The owners moved out because they were being foreclosed on, and the house was listed as a short sale — and it was marked “contingent” the moment it was listed. Then, the family moves back in, and the deal closes after many months. The family never moved back out, to the best of my knowledge.
Not sure if they sold it back in their own name, or if a friend/relative “bought” it back, but there they are. Essentially, people can reduce their principal balances by hundreds of thousands of dollars by doing this. I’ve heard of other instances as well.