Wow Snap/BikeGoddess, that's awful. 
One of the participants in my aerobics class hit her head on the trunk of her car a couple of weeks ago. I forget exactly how it happened, I think she just turned and walked into it. She didn't lose consciousness, but had/has a lot of other concussion symptoms, dizziness, nausea, confusion. Of course a big lump and headaches.
It's weird how the immediate symptoms don't necessarily correlate with the longer-term ones. From what I'm told, I was unconscious for a good 20-25 minutes, and my memories of the next 2-3 hours "flash" in and out, but I didn't have any symptoms afterward other than localized tenderness.
And my LBS still uses the remains of my helmet to show customers what they're for... 22 years later.
Speed comes from what you put behind you. - Judi Ketteler