What factors contributed to enable Rickenbacher to be found?
Actually it was during WW2 and it was the Pacific:


  One of Rickenbacker's most famous near-death experiences occurred in October 1942 [...] The bomber strayed hundreds of miles off course while on its way to a refueling stop on Canton Island and was forced to ditch in a remote and little-traveled part of the Central Pacific Ocean.


I am not familiar with the episode, and this source is currently not working for me, but from the little information that the wiki reports, I have the impression that the main factor has been pure luck.