As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FL400, THE PILOT REPORTED POP NOISE AND FELT A SMALL YAW FOLLOWED BY A SLIGHT LOW PITCH SOUND. POST FLIGHT BORESCOPE INSPECTION FOUND DAMAGE TO THE IP AND HP ROTOR BLADES. DISASSEMBLY CONFIRMED A MISSING 3RD STAGE IP COMPRESSOR BLADE. THERE WAS NO EVIDENCE OF UPSTREAM FOREIGN OBJECT DAMAGE (FOD).