About 35 years ago I was a professional commercial photographer with a photo studio. I was shooting a line of clothing for a manufacturer. We didn't get it done all in one day, so I was asked if it would be alright to leave the clothes in the studio overnight so that we could easily start afresh the next morning. I said sure.
The next morning when I arrived at my studio I discovered the clothes were all missing - but nothing else, not even one piece of the thousands of dollars of photographic equipment. including a camera and lens combo on a tripod worth about $4000 sitting on a tripod just feet away from the clothes. I thought it was odd, and so did the investigating police officers.
Well the clothing manufacturer demanded that I reimburse him for the clothing with a stern letter from their attorney. I had to hire an attorney, who happened to be in my same building, who introduced me to the term "gratuitous bailee". Which simply meant I was not in the business of storing clothes and was only doing the clothing manufacturer a favor, and therefore wasn't financially liable for his loss. My attorney sent their attorney a letter and the matter went away.
In the RV dealership story, I would suggest that the RV dealer IS in the business of storing RV's for repair and is therefore legally responsible for the loss/damage, even if he there are signs posted that claim otherwise. Unless one signs a document to the contrary at the time of dropping off their RV, I'd go after the dealership. A small claims action may be an inexpensive way to make the dealer see the error of his/her ways.