I had a small orange "Occupied" cone taken that had my name on it in big letters. It is amazing what people will take. That was in a high end private campground. Here is a hint, public campgrounds are generally safer when leaving items behind. Private campgrounds with seasonal or permanent occupants I do not trust. I suspect they have a lot of scavengers.
Even something accidentally left behind does not give permission for taking it. People come back for things and the only permissible removal should be by campground staff hopefully with a lost and found bin.
I lost my occupied cone and I lost a mat I was using for a marking spot. I've learned to leave nothing behind from those experiences. If there are no posts for departure date camping receipts I get leery about leaving a campsite when other campers are arriving and never in a self-pay situation. I'm thinking about a cheap sacrificial pup tent for those situations. I've used my large screen tent but wouldn't put it past someone taking it.