In early Season Three, Faith arrives in Sunnydale. However, it isn't long before she disappears; the first of several absences during that period. The first one falls between 'Homecoming' and 'Revelations', where we have the strange events of 'Band Candy'.
Buffy and the others most certainly could have used Faith's help there, but she was nowhere to be seen. Have you ever wondered why she left, where she went, and what she did there?