Object detection in scene

edit savecancel

I follow the tutorial on http://docs.opencv.org/doc/tutorials/features2d/feature_homography/feature_homography.html#feature-homography and got it working perfectly. I'm able to detect images and draw the border around the detected image. I'm having trouble figuring out how to simply know "The image was found" or "The image was not found". Out of all the points and variables calculated during this process, I don't see which one I can use to determine "Yes the image was found". What am I missing? Thanks!