Sounds like something someone on Ambien would do.
Exactly! Here's something from 2006:
from FlyerTalk.com
Was sitting up front MUC-IAD and the FA asked each passenger if they were taking an Ambien for the flight (was very polite about it). I thought it odd and asked why they cared. She said she was on a flight where a man took an Ambien, got up in the middle of night, pulled down his drawers, took a leak on his seat and went back to sleep. Said people were mortified but that she was not allowed to touch or wake him. Guy finally woke up, stretched and wondered why everyone was staring at him. She had to breakk it to him after which he was horrified. I have never had a bad experience on Ambien, but that one takes the cake.