I figured this out from desperation. *wink*
Its pretty easy.. just open your m2 (model) file with notepad and the textures it's using should be readable at the bottom.
What is it for? It helps you locate your textures rather than having to explore them yourself lol. Sometiems textures are re-used by various models and the filenames might be unrelated, since ussually the textures are the same name to their model (eg. mymodel.m2 and mymodel.blp). Also some models use multiple textures.