And much to no one's surprise, it didn't go over well!
Here's what happened:
[Image via WENN.]
When we said he was making the most of his single life, we weren't kidding around!!
The brows in question were raised when Sia's shapely tittays made their debut through her thin black tee (no bra allowed), leaving many to wonder if such a wardrobe faux pas was actually her seduction strategy!
Hmm… think Sia and Robberz shimmied to Justin and Jay later on in the bedroom?
Sound off (below)!!
[Image via Splash News.]