Very hard to believe details wouldn't have leaked out in the last 25 - 30 years TBH
ISINGLASS was a major program - granted it never flew, but advanced and expensive propulsion hardware was built and it was well into the billions in today's money - and >30 years after its termination it was still sensitive. The first time I ever heard the codename, with two read-in participants present, the one who hadn't used the word turned grey and said "You used that word. I didn't."