Hi ginger pom,
Hate to admit it, but I've worked in insurance for almost 15 years...
Given that your friend has obtained the hardest part - the contact details (too many people hit n run these days

), they will get their excess back, providing their insurer decides that they are not at fault. Most likely they have satisfied the requirements of the policy, in so far that they can identify who was at fault and provide contact details. I hope the other guy is insured... there is a thing called the Uninsured Motorist Extension on most Australian policies - basically limits how much can be paid when hit by an uninsured driver - crazy I know cos back home (uk) you can't drive uninsured, but here is a different story. If they do the drive by thing, they will most likely spot the rego at some point. Even then, some insurers will still ask for the excess upfront and then return it later when they have done their investigations. Some claims become a he said / she said type affair, where the two insurers agree to disagree and then each pay their own repairs. Both drivers then pay their excess' which basically sucks.
PM me if you need any further advice.