Since they were missing and only the aide knew it there would have been some undetermined delay of time and action between the president knowing they were lost and going to an alternate or backup course of action what ever that would be,that is, if there is one.
It is the threat of instant retaliation and annihilation that is the great deterrent factor.
If some radical nut case would have had this knowledge and attacked, what could be happening right now is that those of us that were left would be roving packs of animals preying on each other in the dark ages.
Sub nukes aren't on that system, it is useless for them. By the time the subs could be summoned up to a depth where they could receive the codes, the transmitters would be glass parking lots.
It happens that the skipper of a boomer does not launch by himself — other officers must assist to activate the warheads. And they do have orders to cover the situation in which the USA has been nuked and all other retaliatory systems are down. THAT is what keeps the whackos from taking a shot at us.
Only way to neutralize the lurking threat of the submarine fleet is to catch them when they leave port and follow them everywhere they go, so as to be ready to give them a torpedo enema if they open the missile tubes. The fact is, nobody has been able to do this to us, while our subs HAVE done it to those of rival forces.