I see this thread has revived after being dormant from 2006 to 2014, and dormant again from 2014 to 2019. Surely this is evidence that things can survive far longer than expected...
Part of the problem is that the ordinary person in the street thinks in terms of "the age of the dinosaurs" as if it were a single brief period, and not that long ago.
However:
Stegosaurus flourished in the mid-late Jurassic, which was 155 – 150 million years ago.
Tyrannosaurus — another of the dinosaurs that every school kid knows — lived in the upper Cretacious around 66 – 68 million years ago, or roughly 90 MILLION years after stegosaurus.
There was then a period of around 64 MILLION years from Tyrannosaurus to the earliest humans: Homo Habilis, who existed around 2.8 – 2.4 million years ago.
A million is very big — seriously big. People seem to forget that it is 1,000 x 1,000, which is 10,000 centuries.
Could stegosaurus have lived a few million years after the date of the most recent stegosaurus fossil so far found? I suppose so.
Could any species of megafauna have survived 150 million years, through all the geological and climatic changes, and past the meteoric extinction event, so that it could coexist with early humans, and yet leave no further fossil evidence for that entire period? At the risk of sounding sceptical, I'm going with "No."