Ex Miss USA Lu Parker Arrested for Petty Theft at LAX

12:25 PM PT -- A spokesperson for Lu's station, KTLA, tells us the arrest is a misunderstanding -- she noticed the earbuds were left behind, and picked them up, "intending to return them to the owner whom she had been speaking with while in line to clear TSA."

The spokesperson says when Lu was unable to locate the owner, she boarded her flight -- but she is fully cooperating with authorities.

Former Miss USA Lu Parker is under arrest for pilfering a pair of high-end headphones at LAX ... TMZ has learned.

The 1994 pageant winner, and current news anchor in L.A., allegedly lifted the headphones Wednesday morning at the TSA screening area in Terminal 6. Law enforcement sources tell us she walked to her gate and boarded her flight.

We're told cops saw Lu take the audio gear on CCTV cams, and tracked her down on the plane before it left. Officers hauled her off the jet and took her into custody. The headphones are worth $200, so she's looking at a misdemeanor theft.

Really bad luck for Parker -- we're told the owner of the headphones is an LAPD Robbery Homicide detective.

Parker famously dated former L.A. Mayor Antonio Villaraigosa several years ago, but they've broken up.