An arrest requires probable cause to believe that a crime was committed and the person to be arrested committed the crime. It does not require absolute proof. If the witness described you or picked you out of a lineup, yes, you can be charged with a hit and run. If the police investigate and show up to your home and ask you who was driving, you can either give up the name of the driver, or, decline to answer. If they have probable cause to believe YOU were the driver you may be arrested, you may be charged in a report forwarded to the prosecutor, or nothing at all may happen.
There is no way to predict whether or not the police will act on this or what information they might have on you (uh, excuse me ... the driver).
Did you (or, the driver) walk away because you (they) didn't have a license? Had a warrant? Was impaired?