How does Frank prove that Larry was not dead?

Frank prepares a horoscope for Larry at the request of Keller's wife Kate (referred to in the stage directions as "Mother" throughout). She wishes to know if November 25th, the day on which Larry went missing in the war, was a favorable day for her son. According to those who believe in these things (that is, Frank and Kate, but not Keller), it would have been fairly impossible for Larry to die on a favorable day.