No, it is not a silly question, and the answer is quite positive! Yes, people with brain injuries or head type injuries can and do fully recover from their injuries. The time it can sometimes take for such a medical recovery is calculated in either: weeks, months, and even years (rare cases). Many times, there is a fast recovery time soon after the injury, but as time moves forward, medical recovery time slows down. The brain is a very sensitive organ. Some people who have suffered or sustained severe head type injuries show no noticeable problems, while others need constant care for the remainder of their lives! I talk about this situation in the following quick video:
Sometimes a person with a brain injury can remain unconscious and it then becomes impossible to predict how long they will remain this way or when they will regain full consciousness. These of course are in severe accident cases. It becomes very difficult for the doctors to know because the brain is so sensitive, and other factors can influence what happens next. The milder the brain or head injury then, generally speaking, the shorter the time frame for full recovery of consciousness. Likewise, the more severe the head injury, the longer the time frame is for a person to regain full consciousness! It is all about the severity of the head injury.