When you try to perform a mailbox-restore operation to recover the contents of a deleted mailbox in Microsoft Office 365 Dedicated/ITAR (vNext), you can't find a soft-deleted mailbox for the account that was deprovisioned.
Currently, removing the license leaves the mailbox in a hard-deleted state. Therefore, the mailbox is not displayed as either Soft Deleted or Inactive. The following command is specific to removing the license in PowerShell:
When the license is removed from a mailbox without following other deprovisioning steps, this may leave the mailbox in a hard-deleted state. In order to recover the mailbox, the user must relicense the Azure user object. That will reconnect the mailbox as long as it’s within 30 days from the disconnect date.
Customers may find that the Azure user object is missing because they may have deleted the associated Active Directory object on their side. If this is the case, they will find the user object in the Recycle Bin in the vNext Admin Portal. (The customer will be converted to a Cloud user instead of synchronized by Active Directory). The user object can be restored from the Recycle Bin and relicensed to reconnect the mailbox.
As soon as the mailboxes are reconnected, they can be exported through the eDiscovery Export Tool.