Question: is there such a thing as a designated survivor

Answer: Yes, In the United States, a designated survivor (or designated successor) is an individual in the presidential line of succession, usually a member of the United States Cabinet, who is arranged to be at a physically distant, secure, and undisclosed location when the President, the Vice President, and the other officials in the line of succession are gathered at a single location, such as during State of the Union addresses and presidential inaugurations. This is intended to guarantee continuity of government in the event of a catastrophic occurrence that kills the President and many officials in the presidential line of succession, such as a mass shooting, bombing, attack or catastrophic natural disaster. If such an event occurred, killing both the President and Vice President, the surviving official highest in the line, possibly the designated survivor, would become the Acting President of the United States under the Presidential Succession Act.