The Fae never disappeared they just learned to hide themselves. Toby Daye is half fae and works as a private detective in San Francisco. When she is hired to investigate the murder of an old friend it brings up old secrets.
See http://seananmcguire.com/bio.php
Seanan McGuire won the John W. Campbell award for the best new writer at the 2010 Hugo Awards. She uses the pseudonym Mira Grant to write science fiction/horror and the pseudonym A. Deborah Baker to write the "Up-and-Under" children's portal fantasy series.