As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKE OFF, FUSELAGE DOORS MASTER CAUTION ILLUMINATED FOR CARGO DOOR OPEN. DIVERTED. LANDING UNEVENTFUL. INSPECTED THE AFT CARGO DOOR AND FOUND THE HANDLE OUT. SECURED THE CARGO DOOR HANDLE. OPS CHECKED GOOD IAW 52-31-00-710-801 AND DOOR INSPECTED IAW 52-0028. NO FURTHER DEFECTS NOTED. RETURNED TO SERVICE.