I really want to just go put something under the wheels but I’ve never talked to these people.
Update edit: thank you for all the replies. I went over and knocked but no answer. It’s definitely not chocked. If I see them come home I’ll go back over. I’m worried as soon as the weight shifts loading it that it will just go down the hill.
Unless there’s room to back the trailer further in, I don’t think parking a car in front of it is an option. You’d be blocking the footpath.