I know of no such story as "Captain Stormfield's Trip to the Moon."
Mark Twain spent about forty years working on the Captain's visit to
Heaven;  I don't believe that he or the captain took any side-trips
on the way.  Both Mark and Stormfield would be fascinated by these
links between them and the Heaven's Gate group.  I can only begin to
imagine what Twain would say or Stormfield would do.  Twain could
certainly envision folks wishing to leave the planet he re-named "the
Wart,"  and doing via a comet would capture his thinking. In another
story, the character Mark Twain tricks his way into heaven by
switching tickets with an archbishop because humorists are not
welcome there; Twain says elsewhere that there is no humor in heaven,
but he would note not only note the darkness of that event in
California but also its dark humor.  Truly, Twain appreciates the
God's laughter Faulkner exemplifies in -Life in August- when he
metaphorically pulls his camera high above the old farmer who,
carrying Joanna Burden's murdered body from her burning house as her
head, cut ear to ear, falls backward and turns completely around,
says, [paraphrasing]  "Well now, if you'd a-been a-looking that way
when this happened, it might not've happened, would it?"  Capt.
Stormfield's story does not seem exaggerated compared to earthly
events.