As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMOKE AFT LAV WARNING MESSAGE EN ROUTE. SELF-EXTINGUISHED AFTER 5-10 SECONDS. NO VISUAL OR OLFACTORY EVIDENCE OF SMOKE. THERE WAS A LOUD BEEP FOR APPROXIMATELY 1 SECOND AT THE SAME TIME AS WARNING MESSAGE. (FLT 6427) PASSENGER IN LAV AT TIME OF WARNING. INSPECTED LAV, NO EVIDENCE OF SMOKE SMELL. PERFORMED VISUAL INSPECTION OF LAV ENCLOSURE. NO DEFECTS NOTED. LAV SMOKE DETECTOR OPS CHECK GOOD.