Ok, the girl was in a hurry in the lavatory, maybe a gun is an embarrasing object to be "anchored" to the body in all moments of life (a lavatory excursion is another moment in life).
But...
Where was her brain at the moment of LEAVING the lav?
Didn't she take a LOOK around?
And last -but not least- are there many places to plant a GUN in a lavatory to think it could be left UNSEEN at the moment of openig the door and leaving?
