I've run into this argument a couple of times before. Here is my response:
In Christianity, God is known to speak things into existence. I'm not sure about other religions that mention a supreme being speaking things into existence. If God were to speak something into existence, would there be any evidence of an actual cause? I don't think there would be any real evidence of a cause. However; that does not mean that there wasn't one. We know that on the quantum level that particles can appear spontaneously (Or so I've been told, I haven't seen any real evidence of this). So, perhaps, your argument does not really contradict my own. That's one possibility that refutes the "quantum physics refutes God" argument.
It is my understanding that virtual particles require are only obeserved as other particles decay. No matter, no virtual. Is that your understanding?
Observed was a bad choice of words since the particles do not exist long enough to observe them but I think you got the drift.