I've heard of "being followed" by a mountain lion out of curiosity or, perhaps, scavenging when ill, but never a full-day stalk.

There was a recent death in our "backyard" though https://vt.co/news/us/details-emerge-solo-hiker-killed-by-mo... that was, clearly, the result of a planned attack by a teenage male so, perhaps, their behavior is changing.

Still, it's so rare, we don't have enough modern data.