Mystery/suspense - mother trying to find missing daughter, neighbor helps because he also is missing a daughter

[Allromance]

I remember mother hanging posters to find her missing daughter. Don’t recall why dad not in picture. Neighbor starts to help her, he also has a missing daughter from few years ago. He has a mansion and a butler and perhaps a tree house or doll house in the yard. His wife is also out of pic, perhaps dead. He has health issues perhaps, always tired. I read this book around 2008.

[Juels]

Missing by Ann-Marie Richards?