The special does exist. I saw clips from it at YBCA last Saturday, along with several other rarities which made up a program called "Jim Henson and Friends: Inside the Sesame Street Vault". (The
series of screenings was assembled last year by Craig Shemin and screened at BAM in December '09, so anyone who went there would have seen the same.)
The OTL clips looked awesome - vibrant and colorful. "We're in Charge," "Grover Knover" and "The Nighty-Night Show" (Guy Smiley sounded exactly like I imagined when I read the script) ... they left me drooling for more.
The following comes from my email correspondence a few years ago with T.F. ...
Things may have changed by now. Since
Elmo's Christmas Countdown aired on ABC, that makes me a little optimistic about the chances of it being seen again.
So we have proof that the master does exist and has been well-kept. But getting cranky won't solve anything. Being civil and knowing the right people will.