So the patio door was unlocked when you first entered the room? Honestly, if so, I do not see anything to complain about. I understand this as my personal responsibility and my personal security check when I am in the room, especially when being on ground floor.

Or shall they signpost: "Beware, doors can be unlocked" like the advise McDonalds gives you on hot coffee in a cup??

Maybe the American way of thinking is different but in the UK I check doors and windows myself - it is MY and nobody elses safety.