If any of those possibilities were noted in the question I might agree with you. But since we're not told anything about the people, presumably we know nothing about them other than their numbers and locations.
Switch it is still the only moral answer.
As for the question of whether doing nothing is or isn't moral as discussed by Shauna and MILF, it depends. If you do nothing because you have no knowledge of the situation at hand then sure, you're not responsible. But since the situation presupposes that you are aware, doing nothing is still a choice being consciously made. Doing nothing is choosing to let five people die rather than minimizing the casualties and killing one. You may not have set events in motion, but you chose not to save four people when you had the power to do so.
Not a good choice.