You could get a ticket in the mail. It is rather unusual that he would not have arrested you after you failed the field sobriety test. You should contact a criminal defense lawyer regarding this case to ensure that your rights as a criminal defendant are protected and that you understand what your options are under the circumstances.
The statute of limitations for NJ DWI, NJSA 39:4-50 is ninety days. However, NJ law enforcement officers must detain a defendant for 12 hours after a DWI arrest unless they have a ride to pick them up at the police station. Keep in mind that most NJ traffic offenses under NJSA Title 39 only have a 30 days statute of limitations. So it is possible that you may receive another traffic ticket in the mail within the next 30 days.