That happened to us at Yellowstone a few years back. Unfortunately I was stuck in the campground (sick) all day and the folks next door had left their dog all day in the trailer - barking and howling his head off. Lots of campers complaining to the ranger - who couldn't go in because the dog was in no danger (nice, cool, coldy day). However, when the owners got back they got an earful from the ranger and from about a dozen angry neighbors. They packed up and left.....
I frequently see people on this site ask if it's OK to leave the dogs in the TT or RV when they're off running around for the day. I wish everyone here would tell them "No, it is never OK to leave them unattended in a campground." Never. Period.
I refuse to leave my dogs alone in the motorhome, unless maybe it's for a quick run into the grocery store. I'm terrified that something will happen to them. However, you can't always bring them in - but at least make sure you're parked in a location where they have shade if necessary, and they won't be disturbing anyone in a nearby home if they're barking. (I know mine will bark if they see another dog or someone walking close to the camper)