A system is described for tracking a position of a receiver medium as it travels along a media path. A heat source provides heat to the receiver medium in a localized area sufficient to permanently alter a fluorescent agent in the receiver medium, thereby forming a reference mark characterized by a reduced level of fluorescence. A stimulating light source illuminates the receiver medium at a downstream position along the media path, the stimulating light source having a spectrum adapted to stimulate the fluorescent agent to fluoresce thereby producing emitted light. A sensor is used to sense the emitted light from the receiver medium thereby providing a sensed light level signal. The sensed light level signal is analyzed to determine a position of the receiver medium by detecting the reduced level of fluorescence associated with the reference mark.