A missing person was a person who was missing and it was unknown if they were dead or alive. (TV: Fear Her [+]Matthew Graham, Doctor Who series 2 (BBC One, 2006).)
when the Tenth Doctor and Rose Tyler landed in London on the 27 July 2012 they walking past a Lamppost which had missing people posters all over it that were all kids, Rose Tyler said upon seeing them with "what sort of person would do such a thing" with the Doctor replying "what makes you think it's human". It later turned out to be a Isolus that had accidentally crashed on Earth after being driven of course from it's siblings by a solar flare then possessing Chloe Webber and causing the children to be trapped in their drawings. The Children were later released back home when the Doctor and Rose sent the Isolus back to space and to it's sibling freeing Chloe Webber to in the process. (TV: Fear Her [+]Matthew Graham, Doctor Who series 2 (BBC One, 2006).)
All the missing people from Bristol who were taken by the Boneless were put into the walls that was believed to be a memorial made by a unknown artist, possibly one of the victim's family members. (TV: Flatline [+]Jamie Mathieson, Doctor Who series 8 (BBC One, 2014).)
Annabel Arden went missing from some time, but when the trees had done protecting the earth from the solar flares from the Sun they started to disappear revealing Annabel to her mother and sister Maebh Arden with Maebh claiming that she knew she was there. (TV: In the Forest of the Night [+]Frank Cottrell-Boyce, Doctor Who series 8 (BBC One, 2014).)