Witnesses make all the difference man, if you just had one other person come forward and state they saw it happen (and they cannot be passengers in your vehicle) you don't need the other person to claim...
Other info that makes life easier - Get the VIN of every vehicle and plate. Make sure you get the DL # of every driver, and if anyone stops to help or you can just ask a car stopped near you in traffic to act as a witness, life gets a hell of a lot easier.. Everyone pretty much knows to get the insurance policy number, insurance phone, name and contact number of the drivers involved as well.. and a traffic incident report number is handy too.
Insureance companies are supposed to get all this also, but if you do a bit of fact finding right away, they move much faster!
I know Tracy's already stuck.. but this is good info for anyone else... I seem to have the bad luck of getting hit by people a lot... (like 5 times, sometimes they've even jumped the median to tag my car!) so I've been through this a few times..
-=RB