Lotus and Grosjean miscalculated in Q1 and thought they could progress without using soft tyres, a strategy that appeared set to ruin his Buddh weekend and end his run of podiums.
But Grosjean was able to use a one-stop strategy to come through to third position.
"Starting 17th I had no big hopes," he said. "The best strategy on the computer gave me P4.
"I would not have bet a peanut on being third.
"The car came back to how it was on Friday."
After one tactical gamble failed in qualifying, Grosjean said playing safer in the race would have been pointless.
"The race pace was great and we did a very brave strategy - as we did yesterday," he said.
"It was not the time to go safe. It paid off, we're back on the podium."
RAIKKONEN SPAT PLAYED DOWN
Grosjean sealed third with a late move on Lotus team-mate Kimi Raikkonen, who was struggling on fading tyres having run a different strategy.
On the first attempt Grosjean gave the place back again having gone off-track to complete the move when eased wide.
Lotus and Raikkonen exchanged harsh words on the radio before the Finn moved aside for his team-mate.
Grosjean said the row did not matter in the end as it had not cost him his podium.
"Kimi was in a difficult situation and I went for the outside and he didn't see at that point," said Grosjean.
"I knew I had to be careful with my engine and knew [Felipe] Massa had much fresher tyres behind.
"I lost a little bit of time, but never mind.
"The good point is we are on the podium, we scored good points and we still have a very good car for the upcoming races."