Date: 202001
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Aircraft: B777 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction; Physiological - Other; Confusion; Situational Awareness; Workload; Time Pressure
Anomaly: Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Other / Unknown
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Company Policy; Human Factors; Procedure
Primary problem: Company Policy

Narrative: As I returned from [my] last break the [Relief Pilot] in the right seat started his brief on aircraft status. As I settled back into my duty station; the [Relief Pilot] then asked ATC if we were supposed to cross [fix] at 31000 ft. ATC confirmed that we were cleared to cross [fix] at 31000 ft. We were currently at 37000 ft. approximately 4 miles northwest of the fix. The Mode Control Panel altitude selector had never been set to the crossing altitude of 31000 ft. The legs page was correctly set for the crossing at 31000 ft. The Other [Relief Pilot] who was present during the ATC crossing clearance was out of the cockpit taking a final bathroom break as is typical during the crew's final return before top of descent.ATC subsequently cleared us to descend to 31000 ft.; and made no mention of any traffic conflict. We continued on to [our] destination with no further issues. This was an oversight of not properly following SOP during a very busy phase of flight; and forgetting to reset the altitude selector around the same time they were undoubtedly calling back to the cabin to wake the First Officer and myself at the end of our rest period. When I returned to the cockpit neither [Relief Pilot] briefed the descent clearance; I was unaware until the [Relief Pilot] in the right seat asked ATC about the clearance. One major factor in this oversight was undoubtedly due to a passenger in the cabin being in the forward lavatory for an extensive period of time.Our return to the cockpit was delayed much longer than normal; as the passenger was in the lavatory for at least fifteen minutes; and blocked our return to the cockpit after our final rest period. I was resting in a seat and the First Officer was in the lower bunk. We had set the wakeup reminder for one hour prior to landing; which the [Relief Pilots] followed correctly when they called us back; we just couldn't enter the cockpit and had to wait it out. Just as we were getting ready to knock on the lavatory door; the passenger finally came out; and we returned to the cockpit approximately 10 to 15 minutes later than is in my comfort zone; right near [the] top of descent.




Synopsis: An Air Carrier Captain reported during a flight crew switch and cabin distractions they did not comply with a crossing restriction.