Audience tapes of most big rock concerts in the 70s are out there. If 10,000 people were seeing a band, one person likely had a tape recorder with them. Security wasn't tight back then. New tapes old concerts are coming out every day.
Yes, I know but maybe he got a sign from someone who read it in a trader's list or so.
Like we heard it from the shows where only the Thin Lizzy sets appeared so far.
regards
W.