Inconsistent disk capacity reports in OS X - I'm missing 365GB of my 2 TB
Unformatted space.

eg, I have a 500Gb disk with just a 27Gb partition:

   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *500.1 GB   disk0
   1:                       0xBF                         26.8 GB    disk0s1


You can confirm this in Disk Utility or a tool like iPartition.

In Disk Utility click on the drive itself, not a partition of it. Then, under the partitions tab you should see each partition, and then the greyed out freespace available on the drive. You can select it and it'll show you how much you have.