Some time ago, a woman whose blog I read (don't remember who) was describing the reaction of her small child (a bit under 2 years, I think) to Dad being gone on a long trip. The child became very clingy to Mom, who speculated, "I think she's figured out that if he could go away, I could go away too, and then she'd be alone."

Much younger and less capable of understanding than Sarah, of course, but very poignant, I thought, and a good sudden shift to a child's-eye view.