Again thanks to LukasVIE for having posted the link at the top of this forum.
I use it all the time to get my ticket numbers. Burnt last year on reward tickets when AA failed to reissue my companions reward ticket, and had to spend 1.5 hours on the phone with AA to fix, before we could check in. You ALWAYS need your ticket number.
I don't know why AA doesn't fix this - so you can always see your receipt - for reward reservations and other types of tickets.