Anatomy of an Urban Legend: Oliver Lerch Goes Missing

Around the 1890s, according to legend, a Christmas Eve gathering was held on a farm near South Bend, IN. A young man in attendance, Oliver Lerch (or Larch according to some variations), goes into the clear, cold night to get water from the well.
Minutes later, those inside hear blood-curdling screams. They race outside, but find no trace of Oliver. However, in the snow, they spot his footprints. Shockingly, the tracks disappeared halfway from the house to the well.
Suddenly, from the clear skies overhead, the group hears Oliver's voice shouting, "It's got me! Help! Help!" His anguished cries fade to silence within a minute or two.
Much like Ambrose Bierce's "The Difficulty of Crossing a Field," this vanishing into nothing story involves the echoed cries of the unseen victim. And despite iterations showing up in the 1960s (a Welsh version) and in 1936 by Fate magazine contributer, Joseph Rosenberger, who later claimed to another Fate writer that it was all a hoax of his own design.
However, the tale was well-known before then and not likely Rosenberger's creation. The basic plot comes form "Charles Ashmore's Trail," published in 1893 by (not surprisingly) Ambrose Bierce in the volume, Can Such Things Be?
The only real mysteries are how the seemingly unwaiverable name of Oliver Lerch came to replace Charles Ashmore as it took on Urban Legend status (was there something about a REAL Oliver Lerch) and how tales like this and others (The Ghost of U65 or The Bowmen, for instance) are able to leap from the page into popular consciousness as truth?