In my Pokémon I have seen one Pokémon more than caught. How can I see which Pokémon I have only seen and not caught?
Aside from using the Pokedex to check, "seen" means that you actually encountered them. So if you have a good memory, you might remember all the Pokemon that you encountered but failed to capture. Interestingly, Pokemon fought in gyms don't contribute to "seen" like in the main series games.