Vettel took his third title in a row in the season finale at Interlagos after securing sixth place despite a spin on the opening lap of the race.
Three days after the race, however, Ferrari wrote a letter to FIA president Jean Todt asking for clarification on the circumstances surrounding Vettel's overtaking move on Jean-Eric Vergne on lap four of the race following suggestions that the pass may have been under yellow.
The FIA said it had no case to respond as it was clear that Vettel's pass had taken place with green flags on track.
Despite the controversy, Vettel says he was always convinced his pass had been legal as he had seen the green flag.
"To be honest, I never wasted one single thought that an irregularity was involved from my side," Vettel told the official Formula 1 website.
"Even if it was an eventful race I definitely saw all the flags - and their colours!
"I only got information that Ferrari was up to something after Christian (Horner) called me saying that obviously Ferrari was not too happy with the outcome of the race.
"After the FIA had checked every single inch of the recording of the situation in question - and confirmed that everything was according to rules - Ferrari renounced any protests.
"But believe it or not I knew since the chequered flag that there was not a single movement wrong from my side."