What was found
(CAN) ON CLIMB, DURING GEAR UP SELECTION, ECAM WARNING LANDING GEAR AND INTERFACE UNIT FAULT AND GEAR DOOR NOT CLOSED AT NOSE LANDING GEAR. A/C RETURNED TO DEPARTURE TERMINAL. MAINTENANCE CHECK REVEALED NOSE GEAR DOOR ACTUATOR EYE AND LINKAGE PIN MISSING. NEW BOLT INSTALLED AND RETRACTION TEST CARRIED OUT SERVICABLE.