This behavior is by design in the Backup Exec 2012 and above products.
BKF, GRT IMG, and OST media are not displayed by default.

To enable the view of the hidden media for troubleshooting purposes only the ShowHiddenMedia registry key must be created and enabled.

Note: This only provides a mechanism to display the media not to interact with it (By Design). This should only be enabled for troubleshooting purposes only.  Enabling this registry key will display those types of media inside the properties of the disk device, as well as in the All Media node.  The Backup Exec GUI must be closed/reopened for this change to take effect.

Prior to BE 21 - HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Backup Exec For Windows\Backup Exec\User Interface
BE 21 and Later - HKEY_LOCAL_MACHINE\SOFTWARE\Veritas\Backup Exec For Windows\Backup Exec\User Interface

VALUE NAME: ShowHiddenMedia
KEY TYPE: DWORD
VALUE: 1 - Show all media
                0 - Do not show all media

Warning: Incorrect use of the Windows registry editor may prevent the operating system from functioning properly. Great care should be taken when making changes to a Windows registry. Registry modifications should only be carried-out by persons experienced in the use of the registry editor application. It is recommended that a complete backup of the registry and workstation be made prior to making any registry changes.

1. On the Windows task bar, click Start | Run. In the Run dialog box, type regedit.
2. Click OK. The Registry Editor opens.
3. Go to the following key:
Prior to BE 21-
HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Backup Exec For Windows\Backup Exec\User Interface
BE 21 and above-
HKEY_LOCAL_MACHINE\SOFTWARE\Veritas\Backup Exec For Windows\Backup Exec\User Interface
5. In the right hand pane create a new DWORD value called ShowHiddenMedia
6. In the right pane, select ShowHiddenMedia and change the value to 1 decimal. (Figure 4)
7. Close and reopen the Backup Exec console.

Figure 4.

Once the Backup Exec console is opened with registry key enabled or 1 a new Media Properties option is available on the Disk Storage details Figure 5.

Figure 5.
 

In Backup Exec 2012 and above the Backup to disk files (BKF) media, GRT IMG media, and Dedupe OST media are hidden from the Storage Tab in the Backup Exec console. When viewing the "Disk Storage" or "Dedupe" folders no BKF, IMG, or OST media is visible in the Backup Exec console to manage (Figure 1, Figure 2, and Figure 3). Everything in Backup Exec 2012 and above is a backup set view Figure 2. It has replaced the actual view of individual media. The backup sets for all the information is displayed on your device. Storage Tab View Figure 1.
Backup Sets Figure 2.
Disk Storage Properties Figure 3