Magny-Cours was where the Italian's relationship with Renault soured last season after he had the high of winning the Monaco Grand Prix with the French team in May.
Trulli was in third place behind then-teammate Fernando Alonso, who is leading this year's title race, with the chequered flag in sight.
But, as Renault looked forward to having both drivers on the podium in a home race with top management in attendance, Trulli blew it.
While Alonso finished second after starting on pole, Trulli allowed Brazilian Rubens Barrichello to slip past at the penultimate corner and join winning Ferrari teammate Michael Schumacher in spraying the champagne.
Renault were incredulous.
"I simply can't believe something like that, it looked like he left the door completely open," gasped engineering director Pat Symonds - and Trulli announced later that month he was leaving.
"I just consider last year as an experience, as all drivers can do," said Trulli on Saturday.
"Drivers can have different experiences and learn from them. It was a big lesson for me last year and that's it."
The 30-year-old has not looked back, starting the first two races of the year on the front row and securing Toyota's first Formula One pole at the ill-fated U.S. Grand Prix in Indianapolis last month.
In nine races, he has enjoyed three podiums - again Toyota's first - and is well ahead of the man who replaced him at Renault, compatriot Giancarlo Fisichella, in the Championship.
"I keep doing a very good job together with the team and all the engineers and mechanics, so we are extremely happy about our season," said Trulli.
"We've had some bad luck in the last few races as we couldn't get on the podium but we are still here fighting, another good lap today in qualifying, another front row."
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