First World problem and generally lighthearted but a real possibility it could happen.
I've been on a few dates with someone. After a meal we went to hang out at his flat. His flat has an unusual layout where the stairs up to it are in the middle of the actual flat, with half the rooms on each side iyswim. Theres no door or gate at the top of the steep stairs, the entrance door is at the bottom.
Because its so unusual I forgot and a few times over the course of the evening I came inches from falling down them. For context I had a head injury which causes vertigo, so I have to kind of stop and collect myself before going down escalators etc. I've also realised I kind of round door frames really closely, which led to the close calls as it was like I was expecting a floor and there wasn't one 
Short of remembering to sidle along the edge of the opposite wall every time I need a piss, what can I do? I'm not asking someone I barely know to put in a baby gate or anything like that obviously, but they really are steep with not much landing (!) space at the bottom, so flinging yourself down them at speed would definitely be some broken bones or worse.