As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAH - FLIGHT 3749, THE CREW REPORTED A LAV SMOKE WARNING AFTER TAKEOFF. THE AIRCRAFT RETURNED TO IAH WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED THE AIRCRAFT, AND PERFORMED OPERATIONAL CHECKS OF THE LAV SMOKE DETECTOR WITH NO DEFECTS NOTED. THE AIRCRAFT WAS THEN APPROVED FOR RETURN TO SERVICE.