I remember weeks ago when I was researching Pokemon and "Events" of happen on its episodes IRL but on the Pokedex-Bot on Discord, Rhyperior its hard to say IRL I know it takes to add these things but I can be patient
Rhyperior is a generation 4 Pokémon, so as Workbenth said, it's likely it will be added when generation 4 is released
Following on the pokedex bot on discord, is not affiliated with pokefind so it doesn't include just pokemon in pokefind, it includes all of the pokemon in the game.
yeah, its kinda like how pichu isn't in pokemon blue, but it was added later on. Have a great gollying day!