Ours is under the street side closet also (2004 25 Safari). There is a hinged door with no handle on it. It looks like panel only. Open the closet door, put a large bladed screwdriver in the crack on the left side of the panel and gently pry it a little way open. If it is hinged, it will easily open enough for you to stick your fingers in the crack and open it all the way.
Much easier than removing the floor of the closet.
This website is not affiliated with or endorsed by the Airstream, Inc. or any of its affiliates. Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.