Deleting iSCSI LUN did not free my disk space

I had a large (3TB) iSCSI LUN on one of my RN314s (equipped with 4 2 TB drives) that I deleted, and ReadyNAS is not showing the space as available. I have scrubbed and defragged. The iSCSI lun was called Javelin_Migration. I noticed the following while searching the filesystem (note the bold, underlined text):

root@lestatnas2:/data/.purge# ls -tlr
total 0
drwxr-xr-x 1 root root 32 Jun 14 2014 1432681732_Javelin_Migration
root@lestatnas2:/data/.purge# du -k -s * | sort -n
3221225480 1432681732_Javelin_Migration
root@lestatnas2:/data/.purge# cd 1432681732_Javelin_Migration/
root@lestatnas2:/data/.purge/1432681732_Javelin_Migration# ls
root@lestatnas2:/data/.purge/1432681732_Javelin_Migration# ls -tlr
total 0
root@lestatnas2:/data/.purge/1432681732_Javelin_Migration# ls -la
total 0
drwxr-xr-x 1 root root 32 Jun 14 2014 .
drwxr-xr-x 1 root root 56 May 26 18:08 ..
drwxr-xr-x 1 root root 74 Jun 14 2014 .iscsi
root@lestatnas2:/data/.purge/1432681732_Javelin_Migration# cd .iscsi/
root@lestatnas2:/data/.purge/1432681732_Javelin_Migration/.iscsi# ls
iscsi_lun_backing_store
root@lestatnas2:/data/.purge/1432681732_Javelin_Migration/.iscsi# ls -tlr
total 3221225476
-rw-r--r-- 1 root root 3298534883840 May 25 22:32 iscsi_lun_backing_store
root@lestatnas2:/data/.purge/1432681732_Javelin_Migration/.iscsi#


Why is this data lingering, and can I just delete it? I'd rather not format the drives if I can avoid it. I absolutely intend for this LUN and all backups, data, etc to be deleted.

Thanks for your help!