TravelWithKat on "[Plugin: Jetpack by WordPress.com] how do I back-up subscribers"

Yesterday I lost half of my email subscribers. I'm using jetpack plug in.
I use Vault Press to back-up my site but can't see if this backs up subsvribers. Any advice on backing up (and retrievong the ones lost) would be appreciated
Thanks
Kathryn

http://wordpress.org/plugins/jetpack/