As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO SFO DUE TO THE NOSE LANDING GEAR FAILED TO RETRACT AFTER TAKEOFF. THE AIRCRAFT LANDED AT SFO SAFELEY WITHOUT FURTHER INCIDENT. MAINTENANCE FOUND THE NOSE LANDING GEAR SAFETY PIN WAS STILL INSTALLED AND REMOVED THE SAFETY PIN PER AMM 32-00-00-081-001-A.