How to use Subsurface Scattering through a flat surface, and raycasting together?

I have taken this example of subsurface scattering.

Replaced the model with a thin box (with applied sub surf shader), and put two lights behind it to simulate light shining through a thin sheet of white plastic. This works well for my application, however when I put geometry between the lights, the shader seems to ignore the shadow map completely and bleed light through the blocking geometry.

My understanding is that some form of raytracing needs to happen before the light hits the translucent material. Is there a simple method to implement this into the shader?

I have investigated a few implementations of Pathtracers which detect lighting in hope that I could use this as a starting point, like this one:

However getting a scene setup or modifying a scene seems very trival as the project is centred around tech demos with lots of external code. While advanced, I think that this renderer may be overkill for what I am trying to do. I am just trying to raytrace a few spot/point lights through a surface, I dont need to bend the spacetime continuim.

You could make it so the translucent object doesn’t cast shadows (but does receive them), and then just see if the given pixel that you are shading is in shadow.