Disaster strikes on my Debian VM

This morning before work I was fiddling around with my linode, and after a while of things starting to go wrong I decided to restore from my backup!

Big mistake, the VM comes back up but without networking! Further investigation shows my /etc/network/interfaces was back to it's default configuration (auto lo and auto eth0..).. not sure why.

Anyway, after putting the conf back to something normal I discovered there's no ifup command, and using

helium:/home/john# ifconfig eth0 up

also doesn't bring up the interface (as doesn't /etc/init.d/networking restart)

I'm concerned my backups are broken. I'm using the linode thingi which I purchased and set to auto mode about 100 days ago.

Does anyone know what steps I can take to get networking back up? It's fairly important, I run a commercial site on my linode for a friend. I'm not at the moment looking for a perfect solution, I just need to get the linode back online.

Thanks v.much in advance!

Note: the interface seems to be there, but starting it is something else… :/