This link goes to a news article about an amnesiac girl in New York City. Please read it. To sum it up quickly, she is using the name Amber and can quote a passage from Fool's Fate, but does not recall who she is. She is between 14 and 19. She is also quoted as saying that she's writing a story that features a character called Rian “who’s been raised by the commander of the guard post on the edge of a fantasy kingdom.”
Given these details, I think it's possible that she may belong to an online community that shares an interest in Robin Hobb or writing. I've already checked all my friends here at Livejournal and on Myspace, looking for females using the screen name Amber.
If you know "Amber" please contact the New York City police. If her photo looks similar to any online friends who share an interest in my work, or if her story line and character name from her writing sound familiar to anyone, please let the police know.
Some of the comments following the newstories on this that I've seen have been pretty snide and skeptical. I'd prefer to offer help even if I'm later shown to have been gullible.
ETA: She's been identified! :)