Because he wasn't buried, after his death in 1986 at age of 74 L. Ron Hubbard the science fiction writer turned prophet was cremated and his ashes were scattered over the Pacific Ocean.
Scientologists believe in reincarnation and members of church's elite "Sea Organization" allegedly enjoy a 21-year vacation between lives.
So Hubbard's spirit presumed to be on holiday until 2007, when it returns in its next physical identity.
[Added endnote: Do you think he will return as a cockroach?]