A custom scan does not give any indication when a target is missing, e.g. a scan of a external HDD when the drive is not connected, or a scan of a folder when the folder has been deleted or renamed.
The scan will appear to run normally and the summary reports no threats found. There is also nothing in the log to indicate that the target could not be scanned.
The screenshot shows a totally misleading entry reporting "Scan task finished successfully" when in fact the external HDD was not connected.

Bitdefender IS2012 Version 15.0.34.1437, Windows XP SP3