As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: MOMENTARILY LAVATORY SMOKE , ECAM MESSAGE AT ALTITUDE. CABIN CREW INSPECTED ALL LAVATORIES, NO SMOKE PRESENT. UNABLE TO DETERMINE WHICH LAVATORY TRIGGERED THE ALERT. MAINTENANCE ACCOMPLISHED A FUNCTIONAL TEST AND OPERATIONAL TEST OF THE LAVATORY SMOKE DETECTION SYSTEM PER AMM 26-17-00 WITH NO ISSUES NOTED.