Unable to See Exchange Backup since moving to DAG

I am running Exchange server 2013 CU 8 on Windows 2012 R2 and have been backing it up using Netbackup 7.5.0.7 on Windows 2008R2 using a VMware Policy with MS EXchange database option.

Since 27th May we have implemented a DAG and introduced passive mailbox database copies on another server.

Now despite the backups completing successfully, the snapshot, the application state capture step and the actual backup. I am no longer able to find these backups when I try to browse for them. So unfortunately I am unable to recover any mailboxes since May 27 when the DAG was introduced.

Please if anyone has any ideas as to how I can recall these backups, they will be most gratefully welcome.

Or are these backups gone forever, never to be seen again?