The ticket that was ripped up by your cousin was valued at $91. It had a value os that much. If your cousin got a hold of your wallet, and ripped a $100 bill to shreds, would you contact the US Treasury and expect them to pay your hotel bill or buy your gas at the gas station?

So why should Amtrak give you another ticket?

As pointed out, only a few years ago, airlines gave you paper tickets, and gave you both tickets at one time! In fact, you may have even gone to a travel agent and got the tickets 6 months even before your outbound flight!