"She just directed her first film," Brewer captioned the photo. "She had no idea her boob was out. thank you for letting me create magic with you @siamusic."

Meanwhile, though we've seen

"She just directed her first film," Brewer captioned the photo. "She had no idea her boob was out. thank you for letting me create magic with you @siamusic."

Meanwhile, though we've seen Sia out and about without her wig on a few occasions, it's rare.

She explained to James Corden during an episode of Carpool Karaoke that her wig is a symbol of what's missing in the music industry.

"I was a singer for 10 or 11 years to mediocre success," she said at the time. "I was an alcoholic and a drug addict. I sobered up, and I decided I didn't want to be an artist anymore, because I was starting to get a little bit famous and it was destabilizing in some way."