As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT NOT GROUNDED - EICAS MESSAGE: LAVATORY SMOKE; CREW HEARD AND SAW ALARM OUTSIDE LAV 3F-1LC, NO SIGN OF ANYONE SMOKING IN LAV. PERFORMED LAV SMOKE DETECTION SYSTEM OPERATIONAL CHECK PER BOEING AMM DMC-B787-A-26-13-00-00A-300B-A, NO DEFECTS NOTED.