You know I've been starting to think this might be it. The odor is strong and it's like an overdose of the "New RV" smell the trailer had when we first bought it. It's not foul like anything dead. Maybe the guy had it on his clothing when he was working on the winterizing and it got rubbed into the mattress or something. He did have to move the mattress and the dinette cushions to get to the water shut off valves and the hot water heater, so maybe that could be it. I'm hoping that in the spring when I can let it sit with the windows open it will go away. If not I'm taking it back to Colonial Airstream where I originally bought it and had the winterizing done. I've had it for 4 years now and this is the first time I've had this problem, so it HAS to be something related to that visit to the dealer.
Thank you all for your ideas- I'm checking into all of them.