Inadspectusremphobia (From "inadspectus" out of sight in latin and "rem" thing in Latin) is the fear of having something or someone being present but unable to be seen. Sufferers of this phobia mostly fear that someone's watching them without being able to be seen back by them. Or they can also fear that when a person that they know is out of their sight, they turn into a demon or they reveal that they actually hate them. The sufferers can even fear that the ground behind them is collasping at the same speed as they are walking, but keeps turning back to normal when they turn around.
In most cases, the sufferer thinks that whatever is behind them is wrong and whatever is in front of them is normal. They believe that the only exception is when looking in a mirror.