What was found
LAVATORY SMOKE INDICATION ON TAKEOFF ROLL. NO VISIBLE SMOKE WAS PRESENT. DECLARED AN EMERGENCY AND RAN QRH, RETURNED TO FIELD. MESSAGE WAS NO LONGER PRESENT ON FINAL FOR LANDING. PERFORMED ENGINE RUNS, BLEED CHECKS, VISUAL INSPECTION OF ENGINE, INTAKE, AND EXHAUST. NO DEFECTS NOTED. COULD NOT DUPLICATE.