The Police Ombudsman's Office found that she had not worked hard enough to identify the man.
She had been told by bar staff that the man had been drinking and that he had recently been released from prison. But she did not ask who he was.
The collision happened in County Antrim in June 2014.
The suspect drove into the back of a woman's car. She said that he had appeared drunk, and when she told him she was calling the police, he jumped back into his car and drove off through a red light.
The woman and her brother went to a nearby bar and looked at CCTV footage.
She was able to identify the man and said the barman told them his name, that he was just out of prison and that he had been drinking.
The woman said she passed the information to the police officer, but complained that the officer did not seize the CCTV footage and did not respond to her phone calls.
The officer said she had not received messages as her police phone had been left in for repair.  This was later confirmed to be true.
She said she had gone to the bar to get the CCTV film, but was told that an engineer would have to download it.
She left her contact details, but later discovered that by the time the engineer called, the footage had been recorded over.
The officer said she had circulated a possible car registration number to police patrols, but had found no useful information.
It emerged that the woman driver had not recorded the correct registration number.
The officer accepted that she should have asked the barman for the name of the person in the CCTV footage, but said she believed that she would not have been able to progress the case without that footage.
The Police Ombudsman's investigator said that by not asking for a name for the suspect, she had failed to progress an important line of inquiry.
He recommended that she be disciplined.
A policewoman has been disciplined for not asking for the name of a suspected drunk driver who drove away after a crash.