As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW - CAPTAIN REPORTED ON CLIMBOUT LEFT THRUST REVERSER BLUE UNSAFE LIGHT ILLUMINATED. EMERGENCY DECLARED FLIGHT RETURNED DFW LANDED WITHOUT INCIDENT. FOUND UPPER UNLOCK SWITCH INOPERATIVE. REPLACED SWITCH. SYSTEM GROUND CHECK NORMAL OPERATION.