Oddly I really liked this once I thought about and digested it. It was obviously a horrible thing to do BUT, Severus is such an incredibly damaged man I can totally read this as being true. I think Lucius might never truly understand the depths of his fear of abandonment or fear of other's mockery because his life was so very different. But Harry isn't just a normal relationship either--he's the Savior of the Wizarding world, 20 years younger and attractive. So, that would truly cause Severus to have deep seated fear. He's so sure that he's inadequate that it might take something like this to make him truly see he was loved.
I also think that if Harry does realize Severus did it, he knows him well enough that, after the initial mad wore off, he would understand why Severus did it. And I think he would forgive him.
Really powerful stuff girlfriend... loved your use of BFF Lucius.