I found no information on here about this game breaking issue, so here goes...
I learned this the hard way and I'm a bit upset about it, but honestly I would have been extremely pissed off about it if I hadn't already got all my achievements and completed the majority of quests and miscellaneous quests. I also didn't have any other saves to revert to at that point since I had turned auto save back on...and I went exploring indoors, so it saved over my auto saves. Big mistake. *smacks head*
But, I warn you that after you do the quest "Rise in the East" Do not fast travel back to Japhet's Folly, because you will never
be able to fast travel anywhere else from that location. The whole island is outside of the world and once you finish this quest the door that you used to leave Japhet's Folly will no longer be available.
I found out about this a little too late. I wanted to go exploring past locations, and never did I think I'd not be able to fast travel out of a place I recently visited.
So, goodbye to my amazing Wood Elf character...time to work on a new playthrough, which I had intended to do anyway, but still would have liked to have my original character.
For more info check out the UESP notes. HERE