Equalizer:
In my opinion, you're wrong and you're right.

Watermarking has been around for awhile now. I have no idea whether the manipulations you describe would make it go away, but, mathematically, it's possible to introduce stuff to a waveform that isn't "non-audio data" but that still marks it, and is in a detectible form even after major changes. (Of course, I speak in the abstract - I have no idea what the practice is.)

Having said that - you're absolutely correct about the state of the law. It's patently silly to assume that it is worth the time of some lawyer to go after something that small. If copyright violation is proven, they can make you pull that part of the track that violates it. But they wouldn't bother unless they could go the second step and establish grounds for financial compensation - that is, that the new cut owed a measurable amount of its profitability to the fact that one could recognize the commercial value of the original ripped sample within it. Even if such a suit were to happen, a single snare hit's contribution to a song's commercial success wouldn't produce a large enough settlement to make it interesting to the legal eagles.

The music industry is a place where practice and law collide. With the ease and thoroughness of electronic processing, it is almost impossible to define what a copyrightable artistic creation is, exactly, and what constitutes new sound. As a result, what splits the hairs is money, and it's got to be a lot before the lawyer's will even return folks' calls.