The police report says that Tony said Casey moved in with Amy on the 9th. I think Casey was out of the house the 9-15th, Caylee was with GPs, Casey reappears on Father's Day, they fight, and Casey leaves with Caylee who does not fit into her new life at all.
The 9th is an odd day to move, though, isn't it when people almost always move at the beginning of the month?