As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: AFT RIGHT LAVATORY E, SMOKE DETECTOR WENT INTO ALARM IN FLIGHT. A PASSENGER WAS IN THE LAVATORY, SUSPECTED OF VAPING. ALARM CEASED WHEN FLIGHT ATTENDANTS OPENED DOOR. NO VISIBLE SMOKE, PASSENGER DENIED VAPING/SMOKING. MAINTENANCE PERFORMED SATISFACTORY LAVATORY SMOKE DETECTOR TEST PER AMM 26-14-00.