If you were rear-ended and the person that hit you was found at-fault you should not have to pay a deductible in most cases. You should be able to get your damages paid for by putting a claim through the at-fault party's insurance company. They should have at least property damage insurance that should cover the damages to your vehicle.
If you have comprehensive and collision coverage you could submit a claim with your company if you felt the need to. You or your insurance company should then be able to recover the deductible amount from the at-fault party or their insurance company.