Como está escrito na documentação do MS aqui :
The remote device wipe feature also includes a confirmation function that writes a time stamp in the sync state data of the user's mailbox. This time stamp is displayed in Outlook Web App and in the user's mobile phone properties dialog box in the EAC.
informações mais detalhadas podem ser encontradas aqui :
The Clear-ActiveSyncDevice cmdlet deletes all user data from a mobile device the next time the device receives data from the Microsoft Exchange server. This cmdlet sets the DeviceWipeStatus parameter to $true. The mobile device acknowledges the cmdlet and records the time stamp in the DeviceWipeAckTime parameter.
Atualização: Você pode tentar:
Get-ActiveSyncDevice –Mailbox {mailbox name} | Get-ActiveSyncDeviceStatistics | select DeviceWipeSentTime, DeviceWipeAckTime
ou no Exchange 2016 / Exchange Online:
Get-MobileDevice –Mailbox {mailbox name} | Get-MobileDeviceStatistics | select DeviceUserAgent,DeviceWipeSentTime,DeviceWipeAckTime