Exile, unlike other snap-in fans, the Sonata uses the silicone push-pins to fasten the fan to the front lower.
Once you pull the drive bay out, you wil see the holes. Hope you kept your bag of goodies that came with the case, as their are 4 extra silicone pins in the bag for this mounting.
If you are confused about what I am talking about. Look at how the back 120mm fan is mounted.