I think Duncan had a private shower (master bath) off of his bedroom.Yes, he did. I think all the pictures of him and Veronica that were visible when Kendall entered it were meant to reinforce that (and it was totally implied when Kendall tried to hit on Duncan, anyhow).
My only point about the shower was, just saying, "Oh it isn't Logan's hair so it must be Duncan's" can't cut it for me, because if we're to believe Duncan's hair is still in a hotel drain after all this time, then I have no problem believing a previous guest's hair is there, either, or that someone else hasn't used the shower, or that a cleaning person didn't lose some hair in there, etc.
Let me start again.
I just didn't like that they just discovered the Oscar, managed to find the hair on it (planted or not) AND were able to prove it belonged to Duncan Kane who seemingly (as far as we know) couldn't be arsed to get a DNA test to prove his paternity, and so decided kidnapping was a better route.
I accept it. I just don't think it was particularly well done.