As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE NR 1 ENGINE OIL QUANTITY DROPPED TO ZERO FOLLOWED BY OIL PRESSURE DECREASING TO 10 PSI AFTER TAKEOFF. THE AIRCRAFT WAS RETURNED TO LAX WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE FOUND PLUG ON MAIN OIL SCREEN COVER LEAKING. A NEW OIL SCREEN COVER ASSEMBLY WAS INSTALLED AND THE ENGINE WAS SERVICED WITH OIL. LEAK AND OPERATIONAL CHECKS WERE GOOD.