Back-end users can delete devices if they are in either the Off Contract or the No Token status.
Under the Devices tab you will find in the left menu a feature called Deleted Devices.
Here you will be able to find the devices you have deleted, and their current PAC for when you need to re-register them.
Device history
Device history will be deleted with the device and will not be visible again - even when the device is re-registered.
*Note that you can retrieve the PAC of your device on "Device" tab and deleted devices on the left menu. This feature will also enable you to re-register your device if need be.