Justin Bieber Robbery Accuser BUSTED ... By Bat Girl

The jig is up for the woman who accused Justin Bieber of attempted robbery this week -- an employee at the L.A. batting cage where the incident occurred tells TMZ, Bieber NEVER tried to rob anyone ... he never even touched the woman.

The Sherman Oaks Castle Park employee called in to "TMZ Live" moments ago, claiming she witnessed the heated exchange Monday night between Bieber and the woman who was taking photos of him.

The employee says the woman was definitely the instigator, being overly aggressive and ignoring security's requests to stop snapping pics. She says Bieber was upset, but never got physical with the woman in any way ... and definitely didn't try to grab her phone.

Sources close to Bieber tell us, the singer lost his cool because the flash kept distracting him while he was trying to bat.