Not at all...it was in circulation pretty soon aftwerwards and as easy to find as any other show (sound quality quite mediocre, though)
all of the European tour from '98 is pretty easy to find, apart from Tallinn (which i've never seen in circulation) and an audience recording from Istanbul (theres an 80 minute pro shot video, however)
Moscow took a while tracking down but I found two recordings, both of them incomplete though. One was pretty good and the other unlistenable
There are two diferent tapes from the Zagreb show in 1998. One is complete but in a rather poor quality. The other one is incomplete just the first song or so and the second half of the show. But therefore this tape is in a much better quality. Unfortunately I don't think there are any recordings of the 1976 tour shows.
VGP's First Night Stand has a soundboard fragment of If You Can't Rock Me from one of the Zagreb '76 shows - it's about a minute and a half long. I'm sure the rest of it is being hoarded somewhere.