 No, this my point. There is no thermodynamic (macroscopic) flux of energy transferred from a cold body to a warmer one. There is always the potential, but the potential is never realised until the cold body faces an even colder body, or colder surroundings. The only thing we ever observe is the actual transfer of energy, which in a heat transfer is always unidirectional and always (spontaneously) from hot to cold. This is why I asked you about your knowledge of the "thermodynamic limit". Do you understand the difference between conceptually looking at individual ‘photons' and looking at probabilistically averaged macroscopic radiant fluxes? 