There are a number of reasons why Groudon might be missing. You could be in the wrong place, or it has already been caught, or it was defeated.
Groudon is AWESOME!
There is no ruby in groudon.
groudon is better
groudon
Groudon is from the hoen region.
Groudon's cave is in sootoopolis.
At ruby version Groudon is level 45, at emerald Groudon is level 70.
No, Groudon does not evolve in Pokémon Ruby.
the password for groudon on pokepark wii is.... GROUDON: 45594012
Groudon does not evolve, therefore no stone will make Groudon evolve.
you can't find Groudon
Groudon is on level 50.