I had the question today what happens to a powered off VM when the host they are registered against fails? This customer always has multiple powered off VMs and was afraid their VMs would show up as orphaned. I was pretty confident that the VM would be re-registered against one of the remaining hosts in the cluster, but I validated it just in case and this is what the events section of the VM shows:
Relocating from cs-tkmt-h08, emc-vnx-fcoe to cs-tkmt-h05, emc-vnx-fcoe
In other words, the VM is relocated from my ESXi host cs-tkmt-h08 to cs-tkmt-h05. No need to worry about orphaned VMs and manually registering them against the remaining hosts… vSphere does it for you.