is actually rather open ended. The couple had already faked a kidnapping, so it's reasonable to think they could have faked their death too. Or they could have been found, or it could be exactly how "Ranpo" described it... but Momoyama seems to be looking down on Ranpo's early works as "too easy to figure out." Then again, he was also surprised/disappointed by Tachiyama's loss... nothing is spelled out, and the context and be interpreted different ways. This makes it relatively interesting in a way. If the reader wants it to be.