I respectfully disagree in the strongest possible terms. That is one of the things that makes this entire "head hit on the concrete" so very impossible to believe. Even what many people consider a minor trauma, to an adult or to a child can result in some very serious complications and there does not have to show ANY visible damage to head or neck. The person can be just fine, and no one will know that they are bleeding into the brain, or between the dura mater and the brain until they suddenly have altered consciousness and at that point it is life threatening and they may in fact lose substatial areas of brain function forever...That is why even minor sports related bumps on the head, and traffic accidents get sent in for testing around here.'
I am not making any of this up, I promise, so here is a link
When an injury occurs, loss of brain function can occur
even without visible damage to the head. Force applied to the head may cause the brain to be directly injured or shaken, bouncing against the inner wall of the skull. The trauma can potentially cause bleeding in the spaces surrounding the brain, bruise the brain tissue, or damage the nerve connections within the brain.
http://www.emedicinehealth.com/head_injury/article_em.htm