Go up the hierarchy, get Material from Map

Hi,
so I get all bitmaps in my scene using

 theBMs = getClassInstances bitmapTexture

Now looping over scene objects, I want to test if e.g. theBMs[1] is part of the material applied to the current object in the loop. Is there a way to get the material in which this bitmap is in?
I guess I could get all maps of that material and check if any of them is equal to the bitmap, but I thought maybe there is like a function to get it faster e.g.

getParent theBMs[1]

or sth. like that...

Cheers