First I am no Dr. Second you don't necessarily have to hit your head to cause a concussion. That is old out dated thinking. If the body check was violent enough the brain will crash around inside your head. This is often referred as coup, counter coup injury. It just means your brain hit the front of your skull and then the back.

From your description of symptoms it sounds like PCS to me. I would have a more direct talk with your Dr. and see why he/she may feel otherwise. Did anyone at the party remember the event? Could they describe it well enough to assist the Dr. in understanding that this may be the origin of your injury?

What are you doing to help you recover?

What meds has the Dr. prescribed?

What kind of rest are you getting.