i had a maxed out light chaos chao, and then all of a sudden, its goes away. it has an X over it in the moving menu. does this mean i had too many chao in the garden? can i get it back?????

I'm going with a simple game glitch.

Odds are that if you turned the game off and turned it back on (without saving, mind you) and it's still gone, you're out of luck.

Make a new one.