Us Weekly reports Beyoncé's younger sister went missing one hour into the show -- long before the "XO" singer's performance -- and there is no word on why she skipped the rest of the show.
Before going MIA the "Losing You" singer shared a few photos of herself in the H&M tuxedo jacket and trousers she wore to the event on her Instagram account.
Knowles was famously involved in a brawl with her brother-in-law Jay Z after the duo and Beyoncé left the Met Gala back in May. A video of the incident surfaced a week later prompting the trio to release a joint statement claiming all was well between them. The fight also fueled rumors that Beyoncé and Jay Z's marriage was suffering.
Knowles addressed the issue in a July interview with Lucky magazine in which she explained they all feel "at peace" with the statement they put out.