Someone hit my car and then run away?

I don't know who the person that hit my car was and I have no witnesses (Already asked neighbors and they say they didn't hear, or see anything). I already filed a police report and got a report number that I don't know what to do with. The car looked like it was hit very hard; back of it was knocked onto the sidewalk, I think the frame that holds the 2 back wheels together is probably bent because it was hitting the curb when the back of the car was pushed on to the sidewalk. The front left of the car is smashed along with the headlights and the tires got flattened. I have liability insurance from GEICO but I'm not liable because I didn't cause the accident, someone else did... I live in California and I don't want to pay in full for my car to get fixed because someone hit my parked car. I tried to drive it off the sidewalk but it won't get out... My coverages are bodily injury liability, property damage liability and uninsured & under insured motorist but I heard that I would need collision in this situation... What should I do?