View an existing unfolded map?

I am trying to edit an existing UV map for a purchased model. I have done this with other models, but the texture files were such that it was easy to tell from the detail where on a model a particular part of the texture file would map to.

The problem with this particular model's texture file is that it is basically one flat color. I have opened the model in DS4, Gone to File>Send to Hexagon, where it shows up, mapped and all. I want to add detail, particularly weathering, so I need to find out which part of this texture file falls on which part of the model. My assumption was that I could just open it in Hexagon and look at the unfolded map.

Alas, when I do so, there is no unfolded map. The texture files are there, and applied to the model, but I don't know how to view whatever existing unfold lines were created for the texture map to follow, therefore I cannot choose where on the map to add additional detail in a paint program.

Any ideas? Thank you.