Two months ago I was on a "red eye" from LAS to DTW in 3a. Half way through the flight the guy sitting next to me in 3b went up to go the bathroom. He came back ten minutes later smelling like smoke. Shortly later one of the pilots came out of the cockpit and along with one of the FAs asked to talk to 3b in the galley area. I noticed when I got off the plane there were two Wayne County deputies talking to 3b and the FA. There were no announcements on the PA system or any other warnings given that I know of.