He dies you cant get it no more.
get a life<---This guy's mom needs to get a life
The true answer: It dies BUT you can get it back what you simply need to do is... GET A LIFE (joking), beat the elite 4 again and go back to where you found it (Works for every Pokemon like lugia, sudowoodo, snorlax, whatever except roaming Pokemon also suicune will be found under the burned tower instead of Culerean cape)
Chat with our AI personalities
When you knock out a roaming Pokemon, it will faint and then start roaming again, but with its health at full.
If you knock out Azelf in Pokemon Diamond, Azelf will be gone forever (unless you have saved before battling Azelf and shut off the game and turn it back on to try again).
You are out of luck. What you can do is that if you turn off your system and turn it back on, it will take you to where you last saved. From there you can work your way back to Lugia. When you do, make sure to save right before you battle Lugia.
i am not sure but you have to knock treeis with headbut attack
Yes, you get it back righr after the battle.