How to track and freeze picture position inserted in moving video

I am trying to insert a picture into a moving video and to have the picture hold the position where it was originally placed to eventually fall off the screen as the camera pans left. Currently, the inserted picture will pan with the camera movement. the exact effect i am trying to accomplish is the one shown here vimeo.com/1858780 at 27 seconds through 32 seconds...ANY ADVICE WOULD BE GREATLY APPRECIATED!