I lost my iPad, can I track it if the battery is dead?
You can only track it when it is online and connected to the internet.  If it's not online, it could be turned off, the battery could be flat, it could just be out of WIFI range, etc - could be anything.  Use iCloud.com and Find my iPhone to set it to alert when it comes online is all you can really do.

Your best hope is that you were using IOS7 on the device, and had it logged into iCloud, because that way no-one else can use it, even if they wipe the device, without they re-enter your own Apple ID iCloud login.