Casey Anthony's Last Case

Casey Anthony's boyfriend, Tony Lazaro had gone back to New York. He recounts a story about how one night right around then he wakes up and Casey is not in bed. So he finds her sitting on the floor with her laptop crying, watching videos of Kaylee. This is about three weeks after Kaylee has gone missing. Why did no one around Casey ever question the fact that suddenly Kaylee's just gone? What does it mean? And what does it tell us about what happened to Kaylee?"