Usually after removing a iscsi target or making config changes to the software iscsi initiator, the host should be rebooted.
Have you bound your iSCSI vmk interface to the Software iSCSI initiator (vmhba38) at all?
If so it may need un-binding before you can remove the target (although i have to say i don't think i've had to do that before)
(i'm using the vMA to run all of the following commands so vicfg or vmware-cmd commands may not work directly on the host unlless you have installed vcli)
I would put the host in maintenance mode:
vicfg-hostops --operation enter > /dev/null 2>&1
Not sure if you have tried before at the cli as root but I would remove the iscsi initiator and re-add it:
esxcli iscsi software set -e false
esxcli iscsi software set -e true
To un-bind an interface you can use this command:
esxcli iscsi networkportal remove -n vmkX -A vmhbaXX
Here's a small sample from one of my scripts that configures my hosts after a fresh install. Some of the commands may help you.
############# snip ##############
#enable the Software iSCSI initiator on the host
############# /snip ##############
Good luck