Well, the dress has been found ... to be a fake!
The thief who took the gown says he took the dress from Lupita's room at The London after finding the door ajar.
[Image via WENN.]
It turns out the bodacious Barbadian actually used Irish model Jahnassa Aicken as her butt and body double and made her sign a confidentiality agreement that bans her from talking about the gig!
This also wasn't the first time RiRi used Aicken's assets. The 27 year old also appeared in her We Found Love music video!
We're really surprised Rihanna would use a stand-in because she's got a bangin' bod! But whatevs! Well, whatevs! We still love us some Rihanna!
Check out the Armani commercial (above) and see if U can spot the derriere double!