Grand Unifying Guesses/Torchwood

Torchwood 4 is missing because they are...

• In the digital world.
• Dead in the Underground.
  • Alternately, they are down in the Underground. They'll find someone true. Down in the Underground, a land serene, a crystal moon. Yeah. Hah.
• Stuck traveling with a timing device.
• Pulled back in time to help the Minbari. Duh.
• Lost in a Sea of Dirac.
• Trapped inside a Shield World's dyson sphere.
• Just a code named for a subculture of Americans who hunt dangerous paranormal creatures.
• Lost in London Below.
• Lost walking the Silfen Paths.
• On the Island.
• A failed branch of the Special Talent Project
• Were inside of Sunnydale High in '99.
• Hogwarts.
• Contained by the SCP Foundation after getting entangled in a particularly convoluted Temporal Paradox.
• In Northern Ireland. And nobody cares about them.
• In Narnia.
• Trapped on the Game Grid.
• In the middle of the desert in South Dakota.
• Somewhere, over the Rainbow.
• Crossed through the gap in the Wall, wandering the Realm of Faerie.
• Swallowed by a Crack in Time.
• In Canada, no one's just ever bothered to check.
• Hidden in a small town in Maine.
• In Portland, Oregon, staffed by a homicide detective and a reformed werewolf.