As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GEG - AFTER TAKEOFF, THE FLIGHT ATTENDENT ADVISED THE PILOT THAT LAVATORY SMOKE DETECTOR HAD ACTIVATED. AFTER RESETTING THE DETECTOR, IT ACTIVATED A SECOND TIME. UPON SECOND ACTIVATION, FLIGHT CREW DECLARED AN EMERGENCY AND RETURNED TO AIRFIELD. INSPECTION REVEALED NO EVIDENCE OF SMOKE OR FIRE. REMOVED AND REPLACED NR 1 LAVATORY SMOKE DETECTOR, OPERATIONAL CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE.