Hi Stanley,
vMotion is the vCenter Feature, by default if you enable DRS with Fully Automated, based of the Load it will perform vMotion. DRS is a requirement to add a cluster in VCD).
There is no relation between host disconnect and vCloud Director, it s obvious that if a HOST disconnected from VC, all the VCD operation will fail.
Verify the HOSTD and VMKERNEL logs of the ESX host to find the cause, have a look at this article: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1003409