As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT DEPARTED AND UPON REACHING CRUISE ALTITUDE CREW NOTICED LEFT ENGINE COWLING WAS LIFTED UP. CREW RETURNED TO DEPARTURE AIRPORT AND EMERGENCY WAS DECLARED AND THEY LANDED WITHOUT INCIDENT. THE COWL LATCH WAS IN THE LOCKED POSITION, BUT HAD COME DISENGAGED FROM THE COWLING. THE COWL WAS INSPECTED AND FOUND UNDAMAGED. THE COWL INSTALLED AND THE LATCHES INSPECTED FOR PROPER ENGAGEMENT. AIRCRAFT RETURNED TO SERVICE.