* The Event: The Thief event was only available for a limited time in Japan and was never released internationally. This event was specifically for the distribution of a Thief Pikachu.
* No Other Ways: Thief is not available in any other way in Pokémon Emerald. It was never a move that could be learned by any other Pokémon in the game, nor was it ever available via other methods like TMs or breeding.
If you are looking for Thief in other games:
* Pokémon Ruby and Sapphire: Thief is a move that can be learned by certain Pokémon through leveling up or TM.
* Later Generation Games: Thief can be learned by a wider range of Pokémon in later games through various means.
Remember: If you're playing Pokémon Emerald, Thief is not an option. You'll need to look for other moves to fulfill that role in your team's strategy.