Here’s a weird one. From an internal Imagineering newsletter in 1981:
I wonder if they ever found it? I wonder what this “essential set-piece” was – “The Seas” still had no sponsor at this point and wouldn’t open for five more years. At the time this notice was written, the pavilion was intended to be far grander than its final format; its original design included a effects-heavy dark ride incorporating the ancient god Poseidon and the myths of the sea.