I think sports fans understand that when two football players collide and one player is left lying on the field unconscious that they've suffered a concussion. And, they have. But most concussions don't result in blacking out or unconsciousness.
Those of us who are involved in an accident, whether they hit their head or not, walk away from that accident many times feeling hazy, unclear, foggy in their thinking, perhaps not being able to remember immediately before the accident or during the accident or maybe even sometime after the accident. These are all classic symptoms of a concussion and they should not be taken lightly.
I meet clients all the time and explain to them that concussion symptoms may not be as dramatic as being knocked unconscious. Many times there are a lot of factors in our thinking and our brain processing that has been affected by a concussion. It could be depth perception, reaction perception time, or your personality. Someone who has become crabby and upset all the time is certainly, someone who has lost the ability to calculate or think or recall names or be able to do math or find a location while their driving their car or someone who has a headache, or a crushing feeling in their skull could certainly be having symptoms of a concussion.
You shouldn't expect that every person will have every type of symptom, they can be wide and be varied. But the important thing is that if you or someone is having these symptoms, don't dismiss them. You need to make note of them. You need to talk to your physician about them and if your physician isn't taking them seriously, you need to talk to another doctor because these things may go away on their own but sometimes they don't.