Which painting was hung upside down for 41 days, in a US. museum,until someone noticed it?

Mozart, even though this says it hung for 47 days, is this the one? If so, the artist is Matisse.

http://www.brainevent.com/be/WackyWeek/twwih/20011015/index_html

Just noticed that this article goes on the say that this was an urban legend, so either I did get the wrong one or that's what it was.

Good answer Kellygirl.here is my source.Most sites that I've check don't think it's urban legend,and many mentioned 47 days and some 41 days.So who's right?But after looking at the painting I wouldn't be surprise it would be true.