The Rolling Stones rocker, 70, posted a black-and-white tribute photo to
"I am still struggling to understand how my lover and best friend could end her life in this tragic way," Jagger wrote.
He said that he was "touched by the tributes" paid to the late designer and the personal messages of support that he's been given.
"I will never forget her," he added before signing off.
On Monday, a spokesman for Jagger said that he was "completely shocked and devastated by the news." The pair had met on a shoot in 2001.
In February, Scott canceled her
The towering designer, born Laura "Luann" Bambrough, previously worked as a personal stylist for
"I'm a fashion designer. I don't want to be defined as someone's girlfriend," the 6-foot-4 designer once said, though numerous stories about her death tagged her as Jagger's girlfriend, sparking a rigorous social media debate on Monday.
Tributes from her colleagues, clients and critics poured in after news of her death.
"I am deeply saddened by the loss of L'Wren Scott. L'Wren was a total perfectionist, someone who absolutely embodied everything her marvelous clothes stood for: strength of character combined with a confident and powerful style," Vogue Editor Anna Wintour wrote on the magazine's website. "In person, L'Wren was always unbelievably generous, gracious, kind, and so much fun. Her old world American manners and charm were from another time, but her sensibility was always fiercely modern. We will all miss her."
"This is a horrible and tragic loss," I'm so upset. I loved L'Wren's work and she was always so generous with me," pop star Madonna said (via the Mirror).
"The Face" mentor and model Naomi Campbell said she was "deeply shocked and devastated by the news," posting a photo of herself with the designer on WhoSay.
"L'Wren was someone I knew since I was 17. We travelled the world together many times. L'Wren was someone I always loved. She was the epitome of elegance and femininity yet still had a girlish quality," Campbell added. "I will miss her honesty and I will miss her friendship. My heart goes out to Mick and all who loved her and were loved by her. May she Rest in Peace."
Jagger's ex-wife, Bianca, also tweeted about the news.
"Heartbroken to learn of the loss of the lovely and talented L'Wren Scott. My thoughts and prayers are with her family. May she rest in peace," she wrote.
"Rest in peace, L'Wren Scott. You'll forever be missed," said a tweet from designer
"Saddened over the loss of the very talented, generous and always gracious L'Wren Scott. You will be missed," tweeted "Project Runway" judge Nina Garcia.
"L'wren Scott was brilliant, elegant, kind, and generous. ... My heart goes out to her loved ones. What a tragedy," tweeted
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