For those of you who are still doubting, Wikipedia confirms that the little figure you see hanging upside down on the ship is indeed R2-D2.
“Wikipedia confirms” that is about as viable a proof as “I read it in my tea leaves one day.”
I’ve got pictures of the studio model where you can see R2.
you can see for yourself at the smithsonian national air and space museum. They have the actual model used in the film on display just behind the space shuttle Enterprise. R2 is rather easy to find as are a few other Easter eggs the modelers threw in.