I wonder if they even saw it on radar. Is airline radar forward looking only, or is it 360 degrees? The aircraft was an Airbus, one of the smaller ones. A330 maybe, if that's a real thing. There was no evasive action or anything.
Oh, I meant ground radar stations. I'm not sure what evasive action an airliner could take
As for the pilots, I would assume that if they didn't see it someone told them - I mean, you're not the only person who saw it, right?