If you have deleted a device it may be possible to restore it, but this can only be done by Alldevice. In order to restore an item we would need to be able to identify the specific device.
Please provide :-
1. Unique Name or ID of the device, this can often be found from an old report sent to emails.
2. We also need the approval from a person that is approved to request such actions as per the contract.
Tip: Often it's a good idea to not delete devices, but to create a folder such as 'Unused / Archived Devices' and move items there and mark the device as on hold. This way you retain all old history and maintenance logs if ever needed.