Not sure about the context of 'meshes had material IDs set up'. Material IDs/ material assignments only have meaning when creating the project (you can create TextureSets from material assignments), or for baking ID maps from material assignments.
Are you talking about a baked ID map, did you try to bake an ID map from the highres mesh but didn't take the actual highres mesh at home with you?
You need to describe what you have done in more detail.