Maybe a belated deletion from the website helps the perception that the dealer has more inventory or is selling a particular type of RV. I can see where it would be a hassle for a consumer. One would have to call to confirm that the unit is still on the lot.
FWIW, I had a similar situation purchasing a new truck. The salesman told me he would have the new truck on his lot the next day. After a few days of waiting and calling, I searched the Ford inventory in my area and found that the truck had been sold, previously. That dealership lost a customer and I bought a better truck at a different dealership, that same day.