With this third account my second Amex from 2000 immediately showed up the first time I logged onto the website and I requested a card with that Member Since date and that was easy for them to see.
For getting to 1991 (my first account) I ended up calling "both" numbers. The number on the back of the card and the number on credit report.
Neither could find the account the first time I called each number ..... or the second time I called each number.
emails didn't help either.
Then I tried the card-back CS number again and got someone who was able to find the account.
and VIOLA! (or is it VIOLIN? maybe TRUMPET)