Just like a controller should never miss a call....like, maybe, because they're on a landline!
Controllers don't usually have any back up. Maybe an ATSA/ATCA if they're lucky and plugged in.
Flight deck by the nature of most modern airliners require two personnel at all times, therefore should be far less excuse to miss a call. In this instance, both pilots appear to have been caught out for not monitoring ATC. Do not need both to communicate with ground crew.