Fergie was the toast of the amfAR gala Thursday — but it was the singer leading the toasts at the unofficial after-party, the birthday soiree for her friend and agent Sean Patterson. Fergie was honored at amfAR for her work in the fight against AIDS, and she went all-out at the auction, bidding $29,000 for a “Marc Jacobs experience,” which includes front-row seats to his New York Fashion Week presentation and a $10,000 shopping spree. Then she headed to Catch Roof to celebrate with Patterson, the former president of Wilhelmina Models who is starting his own company, and took to the mike to sing “Happy Birthday.” Guests included Jacobs, introducing his new beau, Harry Louis, for the first time, Calvin Klein’s Francisco Costa and Italo Zucchelli, Scissor Sisters lead singer Jake Shears, Andrew Saffir and Daniel Benedict, and a host of handsome male models. Also there was Anderson Cooper, who missed the amfAR bash because he was taping his CNN show. He left at about midnight, pedaling off on a bike unnoticed by the Meatpacking hordes.