The fuller answer
A parent may be absent because of death, incarceration, deportation, deployment, abandonment, hospitalization, unsafe behavior, or reasons adults have not explained. Ambiguous absence can be especially difficult because grief has no clear ending.
A young person may miss the parent, feel relieved, invent explanations, blame themselves, or avoid caring because caring hurts. These reactions can change over time and around birthdays, school events, legal changes, and new information.
Honest age-appropriate information is usually better than vague secrecy, while privacy and safety may limit details. The remaining adults should not make the child responsible for defending or condemning the absent parent.