The woman claiming to have 3 boobs is A FRAUD ... A FAKE ... and ironically what exposed her lie is a crime someone committed against her.

Jasmine Tridevil has been making the rounds, claiming she got plastic surgery to net her an additional boob.

But we got a document from the Tampa International Airport Police Dept. describing a baggage theft. According to the doc ... someone stole a bunch of luggage off an American Airlines conveyor belt, including a black nylon roller bag.

Cops caught the thieves after IDing them with surveillance video. The black bag belonged to Tridevil, but before she got it back it was inventoried by police as part of the case against the crooks.

Guess what was inside the bag? "A 3 breast prosthesis."

BTW ... she told cops the prosthesis was valued at $5K.