A few days later Lucius composed a howler and had Professor Snape deliver it in person to Remus. If the howler wasn't enough to embarrass him, having Professor Snape be the one deliver it and be witness to it should be.

He was quite aware that the professor in question was behind the prank. Only there was no way to prove it. He was familiar with Remus's crowd and the trouble they caused. And this certainly fit into their grand scheme.

Only because of how well timed the prank was set there was no real trace that Lucius could prove and use. That only made him more mad.