Molly Karvinen says the man took about 60 bucks from her tip jar and got on a bus.
She tells a Portland TV station she followed the man onto the bus and demanded the money back.
She says the guy at first offered her a couple of dollars, then finally gave her 20.
Stunned passengers watched the confrontation, until the bus driver told them to take the dispute elsewhere.
Police say they're looking for the tip-snatcher.
