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They did detect it a few days after it reached it closest point. The original data about the discovery is here:
http://www.minorplanetcenter.net/mpec/K02/K02M14.html

so they detected it as it was going away.
that's useful.

Haha, I do agree that that is not really reassuring for next events.

Odd that NASA and the UN have discouraged private space development isn't it?