Sampson didn't enter the draft until 1983, this makes it seem like Red wanted him after his freshman year in 1980. That seems pretty unlikely. No one was leaving college that early at that point (from Dawkins and Willoughby in 75 until basically the early 90's no one was leaving college before at least 3 years). Additionally, while Sampson was very good for a freshman, he wasn't some dominant unstoppable force putting up huge numbers. It just doesn't seem like a very plausible story.
On another note, if that did happen and he did declare, that 83 draft would have been downright terrible with Clyde Drexler at 14 being the only good/great player