According to this page the airframe was donated to Emery Riddle Aeronautical University
The Superstar airframe was later used as the prototype Aerostar 800. The prototype 800 was the Superstar airframe with two more seats (due to a 32” extension of the cabin) and featured two 400-hp. Lycoming engines. The 800 was under development when Ted unexpectedly passed on in 1976. Piper continued development of the airplane as a replacement for their P Navajo but never certified it and eventually donated the airframe to Emery Riddle Aeronautical University.
This is the only reference I can find to the ultimate location of the Aerostar 800.