If I really can't find it, I can try to get AmEx to do a partial charge-back request. I hesitate to do that because, well, this is not a case of the merchant screwing up or not delivering me the promised service. Well, if you consider the travel to be the service, not the ticket, you might be able to argue the case. I'm pretty sure that Amtrak has themselves covered on that front somewhere in the "fine print." Bottom line: I got the ticket. I lost the ticket. I bought another ticket. All Amtrak can be accused of is failing to inform me of the $30 replacement option-which I might well have taken as "insurance" against my not finding the original ticket after all.
* sigh *
Back to re-tracing my steps from end-to-end.