Yes, there is a way. If the export format is pure text, you can go and look into the file itself. Any way, that’s all Unity sees so, even if Blender would give you a number, it would be totally irrelevant.
If you really want to persist in this direction, try a Build modifier. Blender will show in what order the faces are stored in its head. Another totally irrelevant piece of cr… information since only the export file matters.
More seriously. Don’t try to think too hard. If Unity inverts the materials then do it too! Clone your first material, select all the faces with this material, apply the clone, delete the now unused material. Save, re-export… and see what Unity thinks of this new file.
It looks like you stumbled on a bug in the export… or it’s a picnic.
( http://www.internetslang.com/PICNIC-meaning-definition.asp )