So if you have an account, log in to the Amtrak.com website. At the upper left corner there's "My Account". Click on that and at the bottom should be "eVouchers". There's "show eVouchers" which will bring up all open eVouchers as well as used ones for maybe three months after they've been exhausted.
Yes! FINALLY caught that. I've been logging in for I don't know how long and somehow never saw "my account" - I was surprised to see, as you pointed out, that it even has a couple of recent eVouchers I used up with a zero balance. Thanks for the help!