Blue Buckets motorist rights society had filed a complaint alleging that Putin's limousine, accompanied by black jeeps and police on motorcycles, cruised through the empty streets of Moscow on May 7 without a front license plate, Ria Novosti news agency reported.
Video of the motorcade was transmitted live by the country's prime television channels, including Channel One, and is available on YouTube.
The activists, in their complaint filed in May, had sought punishment for the driver, the report said.
Motorists driving without a license plate can be fined up to 5,000 rubles (USD 150) or lose their license for one to three months.
An activist alleged on society's community blog that the city police, despite taking more than two months to reply, could not find the driver as it failed to identify whom the limousine belonged to.
Police did not comment on the video being an official broadcast that clearly identified Putin's motorcade as such, the report said.
Putin's limousine had no front license plate during his previous inauguration in 2004. Neither did then-President Dmitry Medvedev's during his ascension to the Kremlin in 2008, the report said.