Halo 3 Saved Game lost ???

I had some Saved Game trouble today and Xbox.com support told me to hit up Bungie.

I played Halo 3 from scratch the past few days on my new 250GB Xbox 360 Slim (since the game save did not transfer over from my old 360).

Last night at midnight I ended at the start of TRIDENT.
Today I played most of the afternoon and progressed to the finale stage.
I paused and went to dinner and the Xbox turned itself off.
When I restarted Halo 3, the resume solo game reset to TRIDENT.

What happened to all the auto saves at checkpoints, levels starts, etc?

talking with Xbox Live there is no way to get save back.
But why did it happen and how do i avoid it happening again?

I’m sorry, I’d help but I really have no clue.
I hope you find a fix.

Halo 3 doesn’t have auto save.

To save your progress you have to ‘Save and Quit’ rather than just turn off the Xbox.

ODST is the same, played 3/4 on legendary didn’t save at all then the next day I had to start again.