It’s a rule Dean has: wash your hands at the sink farthest from the door. Sam noticed it a few hauntings ago, but he didn’t hassle Dean, just gave some crap statistic about people using the farthest stall catching fewer colds. Dean nodded like that was all it was, just hygiene, sure. Damn germs.
But that’s not it. It’s the carved initials, JW, wrapped up in a sweet little glyph Dad designed himself. To the right of every farthest sink Dean looks: initials, date? Coordinates too, if he's lucky. He’s only found glyphs twice since Dad went missing, both at regular Winchester stops, both from before he left. No good.
He should probably tell Sam, he thinks; College Boy wasn’t around to hear it from Dad. It was just a Dad-and-Dean thing, just in case. But they need all eyes out now, any possible clue.
Any day now, Dean'll tell Sam.