What was found
AIRCRAFT WAS NOT GROUNDED: FLIGHT CREW REPORTED WHILE CRUISING AT FL 330, RED UPPER ECAM LAVATORY SMOKE APPEARED FOR 5 SEC, PLUS AURAL, THEN MESSAGE CLEARED ITSELF. FLIGHT ATTENDANTS IDENTIFIED THE MID LEFT LAVATORY, AFTER PASSENGER USE. MAINTENANCE ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK OF THE MIDDLE LAVATORY SMOKE DETECTOR WITH NO ISSUES NOTED PER AMM 26-17-00.