Missing

Seems like so many are missing these days; people I never knew, aquaintances, fictional characters. What happens to them? What happens to those close to them? How long does the impact last? a lifetime? a few days? does it just randomly enter the mind? the memory. How long do we allow it to have an affect on us? do we have control over how long? How do our minds go about interpreting the impact that a missing person has on us?