RSBM, Whenever someone says there is no rule book for how a distraught parent is supposed to act, I sit up and take notice. There is, actually, a distinct difference in how innocent parents act/react, and how suspicious ones do.
There is a big difference in Desiree Young's actions and reactions than in Terry Horman's.
There is a big difference in Trista Reynolds behaviour, than in Justin DiPeitro's.
Billie Jean Dunn did not do what is expected of a mother of a missing child, and neither did Casey Anthony.
I believe there is a rule book for what worried/grieving parents do, and when someone isn't doing that, (for whatever reason) it's time to give that person another hard look.
JMO