You should totally rip that unmastered version, and upload it for us!
Edit: After some weird googling, came across this page which has something called the "Blue Screen" demo on it, which appears to be the missing tape.
http://somethingscantbeignored.wordpress.com/2011/07/31/park-blue-screen-demo/
This is my music blog I started last year! Thanks for posting the link!! I've still got some old Park stuff to post. The old 7"s and some live shows.
Eric -- Any chance of scoring some of those old Park recordings from ya?