Unlike many concept cars from the 1950s, the D-528 was never destroyed. I saw it in the spring at the Petersen Auto Museum in Los Angeles. The museum's web site's page devoted to the D-528 is here. It describes the D-528 as follows:
"The D-528 was built to test advanced concepts in seating, lighting, air conditioning, and front frame design. The hinged rear fender bulges were functional, concealing a spare tire on one side and a gas tank on the other. Such a design gave the car adequate luggage capacity despite the need to accommodate a large air conditioning system. Although it boasted design features such as a pillarless windshield and Ford’s first reverse-sloping retractable rear window, it was an in-house research vehicle that was never shown publicly. “Beldone” [as it is sometimes called] was a stage name selected by Paramount Pictures for the car’s appearance in the 1964 Jerry Lewis movie, The Patsy, not an official Ford designation."
Below are some photos I took of it.
It's possible that the reason why the D-528 was never formally introduced to the public was that it wasn't all that attractive due to the odd features noted above.