I hear what you're saying on the time troubleshooting the issue... but I find it hard to just put issues aside without FINDING OUT what happened!
I'm not talking about removing the host but the VM itself. Is the VM still running in the old cluster? Are both hosts in the same vCenter? If so, you don't need both hosts to see the same storage, if the VM is powered off, vCenter will do the copying for you. Do both VMs have the same name? if so, this may be your problem.
I don't see why you can't use the VMware converter for an appliance. As long as it isn't a vAPP, you should be able to use it to migrate. I usually only do this if I'm migrating between vCenter environments though. I will try to do everything I can do use vCenter to migrate if it's going from one cluster to another within the same vCenter.