Fighting Faer — Christine Warren

Corrinne has been assigned to investigate and report on a series of leprechaun sightings, much to her dismay. Lucifer is the head of the queen's guard, for Mab, the queen of the Faerie, and he has been assigned to come to this plane and find the queen's nephew, who has been seen repeatedly, and taken for a leprechaun. Luc is referred to Corrinne for information on who he is searching for, only to find that the two of them are inexplicably drawn to each other.

This has been expanded into a longer story in the book Not Your Ordinary Faerie Tale