I had some lights turn on today with no action from a person that I know of. Where can I find a record of what action changed a state and who requested it?
The Logbook shows what Home Assistant did. If something from outside of Home Assistant acted, or if a user clicked on something in the UI, it won’t show any action there though.
Maybe I’m misunderstanding what you mean, but if I turn on my Hue lights outside of Home Assistant (like with the Hue app), “[entity] turned on” does appear in the logbook.
So there’s no tracking data to show how or why? Kind of concerning when entities turn onseemingly by themselves. It weakens the SAF (spousal approval factor) that HA relies on to survive. 
My understanding is that if HA did it then it’s in the database, including the user details, but that isn’t currently exposed.
Of course, if somebody used, say, their Hue app to turn the light on directly, all Home Assistant knows is that the light turned on.
In the recorder database?
That’s what I understand, though I’ve never gone digging.