HELP! I've lost my aTV Flash, gone back to default

Hi all,

I’m not sure what I’ve done but after turning on my Apple TV 2nd gen it has since gone back to it’s default firmware and lost my previously installed aTV Flash.

How did this happen?

More importantly, how do I get aTV Flash back?

 

Reinstal from one of your backups, easy peasy.

How do I do this?