It doesn't change name, it changes type. StreamTecture with ID is a result of preloading/loading image resource. StreamTexture is correct type for texture of the Sprite, so I doubt it is the reason your code is not working. I bet You messed up assigning the reference of resource to actual Sprite. For example You saved preloaded images into a file and tried to load it back from disc in order to assign to Sprite.
Post the code please.