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.]
Looks like someone forgot their skirt is VERY sheer on the sides.
A "Happy" Katy Perry showed off some full-butted underwear as she made her way into her London hotel.
Hey, at least she's wearing some.
[Image via Will Alexander/WENN.]