The Enstone-based outfit had been chasing third place in the constructors' championship over the final races of the campaign.
But its hopes were dashed when Grosjean suffered a spectacular engine failure early in the Brazilian GP and Heikki Kovalainen failed to score any points.
The result may have left the team fourth overall, but Grosjean still reckons Lotus should be happy about a strong second half to the campaign that netted him four podium finishes.
"It was not the way we would have liked to have finished, that is for sure," Grosjean told AUTOSPORT.
"For the guys, three of my mechanics it was their last race, so I would have liked to have finished on the podium and it would have been good to keep the momentum.
"But I think we can still be very proud of what we did in the last few races."
Grosjean watched the race with his engineers and reckoned the front graining that rivals suffered on the green track surface would have played in to his team's hands.
"I don't know what we could have done in the race, but I think we could have been third or fourth if you look at the degradation and our normal pace," he said.
"The car felt alright early on and it was clearly front graining for most of the guys, something we have been pretty good at dealing with if you look at Korea."