Etiquette on contacting past owner of your new RV

Steve is completely correct, the dealer has no say in the issue. As the coach was at a dealership, it was probably traded-up from....
That said, they prpbably have good memories of that coach. So, if you call and they don't throw the phone down (very unlikely), then be ready to be on the phone a very long time and maybe make a new friend.

This happens in the sailboat world all the time.

Matt