There is an API function for just this expect that it requires the polygon id that the uv coordinate resides on:
getPointAtUV (int polygonId, MPoint &theClosestPoint, float2 &uvPoint, .....)
Return the position of the point at the given UV value in the current polygon
And I don’t know of a fast way to query that when I am looking up a uv coordinate and not an actual uv index. The only method I have come up with is to iterate over all the polygons and put that lookup in a try/except, since it will error if the uv does not exist on a given polygon.
I could also loop through all polygons and query their uvs to see if my reference point is contained within its boundaries. That actually might be the next thing I try.
Does anyone know of a better way to get the polygons associated with a uv coordinate, or even a different way of approaching this?