I don't believe in heaven, however the Christian concept doesn't have people, but souls in heaven. A soul is a spirit, and a spirit is a ghost.
From Wiki
"As such, much of the
Christian Church considers ghosts as beings who while tied to earth, no longer live on the material plane.
[28] Furthermore, some
Christian denominations teach that ghosts are beings who linger in an
interim state before continuing their journey to
heaven"
The concept of ghosts are "lost souls" of the dead who've remained on Earth for whatever made up reason.
Notice no one ever saw the ghost of a living person.