On Pokemon Sapphire where do i go to capture the pokemon with the blue crystal

ive already found the huge pokemon to use the big blue gem on him…but team aqua or whatever used the red gem and scared him away.
what do i do now???
how do i find him to caputre him with the master ball??

You can get it in sootpolis city. First, head straight up to find yourself at the gym. You can’t enter now,
so go west and then north to enter the Poke Mart. Buy fifty Ultra Balls
(yes, fifty) and then exit. Go north here and follow the path and you’ll
spot Steven and another man, who will introduce himself as Wallace,
Sootpolis’s Gym Leader. After some talking, they’ll tell you to go into the
Cave of Origin. Enter and then head straight. You’ll find yourself in a
darkened room, so use Flash to lighten it up. Make your way around the cave
and grab the Poke Ball when you see it to get HM 07, Waterfall. Now when you
get to the room with the legendary Pokemon, SAVE YOUR DAMN GAME! Then
approach it and stand in front and it’ll slowly approach you. You now enter
battle! (This Stuff Is From GameFaqs.com, the best Faq Site ever)

Aqua Blue Crystal
Aqua Blue Crystal
Aqua Blue Crystal