My original point stands. We haven't observed vN-B probes. This negative result is useful in a Bayesian way; it makes it less likely that the galaxy is full of tech civilizations, and makes other possibilities more likely, including several that you mentioned in a needlessly belligerent fashion.
For anything more than 10^6 km away and less than 10 metres in size, we just wouldn't see it. We have only just noticed some enormous lumps on Ceres, and it seems a whole planet has evaded detection until now.
I don't think it's particularly likely we will find a vN probe. But to consider their non-detection to be of statistical significance is, I think, an overestimation of our technological capabilities.
