I was able to get replacement glass for our 2009 25' FB Flying Cloud from our local (Portland, OR) AS dealer. He had it in stock so it was just a matter of driving down to pick it up. It came with the brackets that the open/close arms fit into and the top "hinge" pre-installed.
Perhaps your dealer misunderstood what you were asking for. I wouldn't think you would need to buy both the glass and frame to get the glass.
If you don't have a parts manual, you can get it from the Airstream web site as a .pdf file for free. In it you can find the part number for the glass and, better yet, be looking at that page when you talk to the parts guy. Most likely he'll be looking at that same page on his computer!
"To err is human, to air is devine."