TLDR; Most are owned by Bob Ross, Inc., who aren't selling them currently. Also, some unknown number is in the hands of individuals who don't know they own a Bob Ross, the article is very vague about this. Not in the article, but it's actually not nearly impossible to buy one. In fact there's one on sale right now for a cool $95K at the Modern Artifacts gallery, who specializes in Bob Ross paintings.

I really, really hate this style of article. Here's a question, but before we answer it, here's 25 paragraphs of blather.