Vettel said he realised what had happened on the penultimate lap and sent a radio message to try and help avoid confusion.
"Fortunately, we had radio and we had the lap counter in the car and my pit board was accurate," said the four-time world champion Ferrari driver.
"But if you lose radio and maybe the pit board is not there, then you back off and being in the lead, you hope all the others back off as well.
"I was just worried. I told them on the last lap, so people don't jump on the track, waving flags and celebrating, because we are still going at full pace.
"I even watched it on the TV, on a trackside screen, and after I saw the flag it said 'final lap' on the graphics so then I was a bit confused.
"I told them the race isn't over yet and they said 'no, keep pushing' and I saw some of the marshals were celebrating. They peaked a bit early!" Frenchman Pierre Gasly of Toro
Rosso, who finished 11th, said the flag's early appearance was "risky".
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)