Here's why:
* JewelBeemon is not a digivolution of Stingmon. JewelBeemon's digivolution line is different, and it's not even a playable digimon in Digimon World Dusk.
* Digimon World Dusk has a limited digivolution pool. The game focuses on certain digimon and doesn't include all the possibilities from the anime and other games.
To get a JewelBeemon in the game, you would need a different Digimon. However, JewelBeemon is not a digimon you can acquire in Digimon World Dusk.