some more questions and observations - spoilers
There is a difference in the address for the daughter. Early the mother gives the address as 154 Pereire Blvd in the 17th when talking to the police. The letter he sends the daughter (but is in the hands of his polish lover)at the end is 174 Pereire Blvd.
Is the polish girl his daughter? The village she talks about being in Virginia from his novel is actual a lovely village in Poland where she was from. The picture of her father standing next to a car was vague but looks like Ethan Hawke.
The french lover (who looks like an older version of his wife) had a daughter killed by a driver that she later killed in revenge. The picture of the daughter looks like the picture the polish girl showed Hawke when they were in bed.(she was wearing the Christmas dress by her mother). Could Hawke really be her husband. SOme creepy Oedipal and Electra overtones here.
To explain the disappearance or the daughtey, Maybe she is mentally ill like her father and had a dissociative experience and wandered into the forest by herself.
Just rambling, help me out here