Alicia Keys held her annual Black Ball charity event in London Wednesday (June 15), but when a certain big named attendee failed to show up she had no problem calling him out.

Keys, who hosted the event to raise money for her Keep A Child Alive foundation, which provides medicine and funding to those suffering from HIV and AIDS in Africa and India, took to her Twitter page to lash out at '80s music star George Michael for not showing face. "#Blackball Uk was a TREMENDOUS Success!!!!" she wrote. "but one question...what kind of person bails on 15million orphans...#GEORGEMICHEAL???? ;-(," she wrote.

Michael was billed to perform at the event, but was forced to pull out at the last minute, due to a toothache. "Hi boyz n girls...bad news im afraid. This tooth ain't getting better in time for tonight, not enough to sing anyway," he wrote to more than 180,000 of his followers.

Perhaps Keys wasn't aware of his reasoning for not attending before she called him out on the social networking site because she has since removed the post. Prior to him pulling out, Keys was singing the praises of the 47-year-old. "I'm honored that George has lent his voice to our KCA cause and I'm so excited that he's singing for us at the Black Ball in London," she said in a previous statement. "It's going to be an amazing night!"

Keys co-founded Keep A Child Alive in 2003, alongside longtime AIDS ambassador Leigh Blake. Last year, the new mom spearheaded the Buy Life initiative, calling on the likes of several of her famous friends to pose in T-shirts donning a bar code for consumers to scan and donate money directly to the organization.