Dude, that sucks! I'm glad to hear you're not more injured. Hits to the head can be scary. When I hear about stuff like this happening, it makes me wonder why anyone would refuse to wear a helmet.
I've had numerous crashes where my helmet did it's job and took most of the impact. Two times I ended up with a huge headache, but no concusion. THANKFULLY!
I've heard both sides of the helmet/no helmet argument for bicyclists AND motorcyclist. To me, it just makes more sense to have it on, then not have it and wish you did.
What kind of helmet do (did) you have? Bell and Giro have crash replacement policies. If you get another Bell/Giro, you ought to look into it. It'll save you some $$$$.
L8R
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"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming, "WOW, What a Ride!" - unknown
"Your Bike Sucks" - Sky Yaeger