Rihanna on Jay-Z & Beyoncé's wedding: "No one knew!"

Rihanna was just as shocked by Jay-Z and Beyoncé Knowles' secret wedding as the rest of the world.

"I didn't know!" Rihanna said. "No one knew!"

Though the nuptials are yet to be officially confirmed, sources close to the couple say the ceremony did take place April 4 -- and Knowles, 26, has been spotted wearing a huge ring.

Rihanna -- speaking at the Escada Moon Sparkle/Island Def Jam benefit for her Believe Foundation and DKMS, the world's largest bone marrow donor center -- also spoke of her rumord boyfriend Chris Brown, who was in the audience at Manhattan's Highland Ballroom.

"Chris said it was a good show," the 20-year-old told People.com. "He really enjoyed it."

After the show, the 'Umbrella' singer, real name Robyn Fenty, met with several young bone marrow transplant patients. "You are so beautiful," she told 15-year-old Camila Mera.