I do see why you (and others) say this. The spot was obviously well-hidden.
What doesn't make sense is that a killer leading his victims through a creek would make the entire crime more difficult, uncomfortable, and risky. If he did, in fact, park at the CPS building, he'd have to make his way back while cold, wet, muddy, leaves sticking to him, and maybe bloody. Why plan it that way? And why let Libby's shoe remain visable (unless he wasn't aware it came off)? Maybe this really is what made it "odd" and "physically strange." Planning a creek crossing definitely would be.