It's likely you're thinking of another Pokemon game where Lugia is available.
Here's where you can find Lugia in other Pokemon games:
* Pokemon Gold/Silver/Crystal: You can find Lugia in the Whirl Islands after defeating the Elite Four.
* Pokemon HeartGold/SoulSilver: You can find Lugia in the Whirl Islands after defeating the Elite Four.
* Pokemon Omega Ruby/Alpha Sapphire: You can find Lugia in the Seafloor Cavern after defeating the Elite Four.
* Pokemon Let's Go Pikachu/Eevee: You can encounter Lugia in the Seafoam Islands after defeating the Elite Four.
* Pokemon Brilliant Diamond/Shining Pearl: You can encounter Lugia after defeating the Elite Four and exploring the Spear Pillar.
* Pokemon Legends: Arceus: While not directly catchable, you can find Lugia in a post-game event and view it in the Pokedex.
If you're looking for a legendary Pokemon in Pokemon Vortex, you'll want to check the game's specific guide or wiki to find out which legendary Pokemon are available and how to encounter them.