Not your fault but Next time you are in Nat park or Nat campground ask if they have any "campground Occupied" signs. We picked up 4 at Yellowstone. I think 50 cents each for a cardboard 10x12 sign. Get some and stop by staples or such and have it laminated. Then for about $5.00 pick up some yellow plastic chain (home depot etc) 10 feet is maybe 1 pound.
Then when you leave your campground drape one end on your campground post and other end on something.
A lot of people just see an empty site if no RV is there.
Short story..we were at the 1000 trails near Astoria, waiting to check in. This guy walks up to the guard house and said "we found a campsite but the previous people left some chairs. If you (the guards) have their phone number maybe you can call and they can come back for them". Guards explained that chairs were left so others would know campsite was occupied. The look on the guys face:)
Bottom line...some people just don't know if a vehicle/RV isn't at a campsite.
And some places have "campsite occupied" signs you can borrow.
2003 Majestic 23P... Northwest travel machine
2013 Arctic Fox 25W... Wife "doll house" for longer snowbird trips
2001 "The Mighty Dodge"... tow vehicle for "doll house"