Is there a possibility that the source for this alternate creation story could be found in non-biblical references? That would be a strong support for the alternate theory.
Of course, oral history presents a challenge, in much the same sense that translation does (as you have noted.) One possibility is that prior to being put into writing the oral history was passed down from Adam to the flood. Then, with only 8 souls surviving, the oral history was retold. How much "drift" could the story have taken over about 1500 years? As there was an angel in the garden, or there were cherubim with flaming sword in the garden (to guard the way of the tree of life,) or there was God in the garden to pass the penalty for the decision that Adam and Eve made. Could it not be that one teller, not of the line of Shem, got confused and related that there was "something about a cherub and someone getting kicked out."
We read in the Book of Mormon that Angels appeared to Korihor, for instance, and told an entirely different version of the "gospel" than was true. We are told that Satan went into the land and told the sons and daughters of Adam and Eve to "believe it not." It is not much of a stretch to me that all through history, wherever there was a narration of the Garden of Eden story Satan would do what he could to transform the truth into a fable. It is one of his methods.
So there could be, by this line of thinking, that there could be many creation tales, each stranger than the next. The origin according to Shiva in Hindu tradition. The biblical version of God, the version held by the Chinese. The version that trickled down to the native Americans about mother earth and such. Like the old gossip game, the telling and retelling could so distort the original story that it would be difficult to discern that the source material, the "truth" if you will, was all the same.
A scholar could identify the similarities and declare that all were myth. Another scholar could select one and call it true and the others myth.
What we have in Genesis and the Book of Moses is the version (reasonably the "true" version,) as told to Moses by God Himself. That version was put into writing, probably soon, but certainly during the lifetime of Moses. That story was handled by one one reporter. Other stories clearly would have been passed down through at least 500 generations before being written down - if, indeed, they were even written then. Some creation stories among native americans and africans weren't written until anthropologists took on the task of writing the histories as related by a tribal historian or shaman.
What is the most probable accurate version?
Walt