SpriteFrame _textureFilename empty?

Hi,

I want to get the sprite frame name for a given sprite in my game.
I looked at cocos2d-x code and saw this is stored in the SpriteFrame of the Sprite under _textureFilename.
However if SpriteFrame::initWithTexture is used to create the SpriteFrame, which is the case in my game, _textureFilename will be empty.

Is there any other way to know the frame name for the displayed frame of a Sprite under this circumstances?