for rent by owner

A few weeks ago I saw a sign in front of our neighbor’s house “for rent by owner”. Unfortunately the neighbor who lived across the street from us for more than a year has moved out. The house is empty now and I do not know why I did not noticed when they moved out from their house. They were not my friends but for the year that we were neighbor it seems that they were good people. I did not talk to them only to say “Hi and Hello” when I saw them in their drive way. I wonder where they moved. I just hope they were okay.