Sorry, but Alan is right on this one. The Auto Train was the first to go e-Ticket, but the e-Ticket system is different than the one used by the rest of the system (and the Amtrak app and Passbook).
All you need to do is drive up to the gate, give them a reservation number and ID, and you're in.
The process:
http://www.amtrak.co...etless-check-in
Based upon my recent experience this past July, they didn't even want a photo ID or the reservation number. All the attendant in the booth wanted was my name. In Lorton they already had little Auto Train booklet that describes things about the AT and provides a place to write the car numbers labeled with my name on it. In Sanford they look on a computer list for one's name. But in both cases, no ID or reservation number were requested.
When you go to checkin inside the station, there they want photo ID, but nothing more. I never even showed any paperwork or reservation confirmations at all.
Now, one oddity that I did note is that the portion of my family traveling on a paid eTicket that did not and will never go into the Amtrak App or Passport, was done once they checked in with the photo ID's. For those of us traveling on an AGR award, the agent's computer did spit out standard Amtrak tickets which I was asked to sign, and then she returned the stubs to me after pulling the tickets.
I'm not sure why they're doing this odd procedure at the AT for award reservations, but it is what it is. But in general, the AT has gone ticketless and there is no need to present any paperwork. And again, the eTickets do NOT show up in the Apps because they don't use the QC codes and the conductors don't lift tickets.