Dermot Weld's five-time winner looked like she might bow out with victory when taking over from long-time leader Rajinsky, travelling smoothly, as the field entered the home straight.
However, her challenge ended at the two-furlong pole when the Jean-Pierre Gauvin-trained favourite Iresine came past with a winning run and stayed on strongly to the line to back up his success in the Prix Foy and also provide jockey Marie Velon with her first Group One victory.
The Moyglare Stud-owned Search For A Song plugged on gamely for the silver medal and trainer Dermot Weld, who was in the French capital for the six-year-old's swansong, was full of praise for the daughter of Galileo as the curtain came down on her on-track career.
He told Sky Sports Racing: "I'm delighted, and I've been honoured to train her. She's been a wonderful mare to train and she's done us proud. She's won two Classics, a couple of Group Ones, multiple Group One-placed and she was champion staying filly in Europe two years running.
"For a six-year-old I'm so proud of her to come back and run a cracking race - full marks to the winner, he must be a very good horse.
"She's been a very genuine, tough staying mare. The winner is rated 118 and she's put up a wonderful performance as she always does. We're very proud of her."