Created an ON_MESH_POINT on an edge, which face it belongs to?

I am working at co-planar intersections between line segment and triangle.


Shown as picture above,
How to determine which face it belongs to? Did \mathbf{P}_{isect} belongs to both \mathbf{F}_1 and \mathbf{F}_2 ?

I am not familiar with SetFacePoint and SetEdgePoint and got a little bit confused by the annotation:

“When m_ci refers to a vertex, any face that uses the vertex may appear as m_face_index. When m_ci refers to an edge or m_edge_index is set, then any face that uses that edge may appear as m_face_index.”

I create it by code below:

// get intersection parameters...
ON_IntersectLineLine(pq, isectEdge, &t_pq, &isectEdgeParamT, 1e-6, true);

// create a ON_MESH_POINT on the intersection edge
ON_MESH_POINT isectPoint;
isectPoint.SetEdgePoint(mesh, p.m_face_index, isectEdgeIndex, isectEdgeParamT);

@piac - is this something you can help with?