It's not based on a true story. The plot and characters were crafted by the writer for creative purposes rather than being drawn from real-life events.
Well, 'unseen' might imply that it's something that has not received a great deal of attention yet. When it's 'based on true story', it indicates that the core or some elements of it are drawn from real - life occurrences. For example, there could be a small - scale documentary about a local hero that not many people have watched, but it tells a real story from that area.
One example could be some local historical reenactments that are only shown in small community theaters. They are based on true events in the local history but are not widely known outside the community.
I haven't actually read this specific story. But generally, a story about an unseen patient could involve things like a presence that the medical staff can't physically see but can sense in some way. Maybe there are strange noises or events in the patient's room that seem to be related to an invisible entity.
Sure. One type of unseen footage scary story could be about a group of people exploring an abandoned place. They set up cameras to document their adventure. Later, when they review the footage, they see things that they didn't notice while they were there. Maybe it's a shadowy figure that moves in a way that's not human or strange noises that seem to have no source. It gives a sense of dread because they were there and didn't know they were in danger.
The idea of an unseen patient is spooky in itself. It plays on our fear of the unknown. We can't see what is causing the strange happenings, and that uncertainty is terrifying.