As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAKEOFF, A KEY LEFT IN THE CREW DOOR DEPARTED THE LOCK AND WENT INTO THE LEFT ENGINE, CAUSING A LOUD NOISE WHICH ALERTED THE CREW TO AN ENGINE PROBLEM. THE PIC REDUCED POWER WHICH CAUSED THE ENGINE NOISE TO BE GREATLY REDUCED. THE CREW ELECTED TO RETURN VFR TO THE FIELD WITH THE GEAR AND FLAPS DOWN AND LANDED WITHOUT FURTHER INCIDENT. TEXTRON-GSO WAS CALLED TO EVALUATE THE LH ENGINE DAMAGE.