Determining the Face of a collision

Is there anyway to determine the face/polygon where an object has registered a collision. My class derives from shapebase. I need the vertices of the face so I can determine the plane it lies within.

I need to do something like:

for each collision point
  determine the face on the object where this collision point lies

Im using mConvex.getCollisionInfo(); to get the collision info.
This sets mCollsionList so I can access each registered collision by mCollsionList.collision[i];

The Collision structure has a field for the face, but as stated in the declaration:

// Face and Face dot are currently only set by the extrudedPolyList
// clipper.  Values are otherwise undefined.
U32 face;     // Which face was hit
F32 faceDot;  // -Dot of face with poly normal

So does anyone know of a way to determine the face on the object corresponding to each collision point. Or does it look like I'm going to have to code this in myself.