Unformat a dive

Hi all,
I need your help!
I had a Raid 1 system 2TB+2TB.
As the first volume sent the message that should be replaced, I purchased a new one. I replaced it (WD). Nothing happened. I understood that as automatic rebuild was ON, the system should begin the mirroring. After several reboots nothing happened and the NAS always said bad disk (1). I tried to format the disk from the tool of the NAS and I chose to format Volume 1 (the only shown drive, that I thought - wrongly- was the new drive). But it has formatted the second drive (the one with the data) so now I have a 2TB disk formatted data. As soon as it rebooted I realized the problem and stopped the NAS. I have written nothing in the drive.
Now I have lost all the data unless there is a way to unformat the drive.
Does anyone know if this is possible?
Thanks in advance,

David