I saw it at the Musee d'Art Moderne in Paris in the spring of 1976. It wasn't in the washroom. It was out in the middle of the exhibit floor along with some other pieces. People were sort of walking around it stroking their chins trying to figure it out, as if they were going to figure it out just by looking at it. Here is a hint: it is a urinal. Someone mentioned above that the original was lost and they substituted a copy. The one I saw had "R. Mutt 1917" written on it as plain as day. If a museum can show a fake urinal with a fake signature, I don't know why anyone is worried about Photoshop. Seems like we have bigger fish to fry.
They were also exhibiting Duchamp's copy of the Mona Lisa with a moustache drawn on it. It is titled L.H.O.O.Q which is pronouced "Elle a chaud au cul" which translated means "She has a hot ass." Since Duchamp manipulated the Mona Lisa, no one knows if the one with a moustache or the one without a moustache is true, so everyone has lost faith in art.