The lady who wrote the anonymous note came over to speak to us. She was really touched by how unhappy the dog sounded and wanted to let us know ... her intent was not to threaten us with a report to Front Desk. There are a number of people in this loop who rent for many weeks at a time so they do spend many days at thier site instead of the parks. She does not have a dog - but don't ask me why she is on a pet loop?!?
We turned on the radio for company and also to mask the sounds of people talking as they walked by the RV; also to block the sounds of other dogs barking in the area, fireworks, etc. which could trigger him to bark, too. We never meant the radio to hide the sounds of our dog barking.
Then we sat outside at the picnic table. Checked in on him periodically. No barking. Then we rode the boat to MK and back, had lunch at Trail's End and came back to the RV - no barking when we came back to the RV, he was in his bed sleeping.
We have been very patient with a dog that has had a rough time since losing his brother. We would not have left him if we didn't think he had improved. He was having a bad day.
Lessons we learned: on the first day in FW, don't leave him too long. Leave him some company in the form of the radio. Stay on his schedule: he eats on demand (food in his dish at all times) but expects treats on a regular schedule.