It's been a long time since, I read it, but in Bob Colacello's biography[1][2], I thought he mentioned that Warhol did create (or at least _refer to_) items as "ready made art", without (if I recall correctly) reference to Duchamp.

But I could be mistaken.

[1] http://en.wikipedia.org/wiki/Bob_Colacello [2] http://www.amazon.com/Holy-Terror-Andy-Warhol-Close/dp/08154...