Was the OP aware of the terminal change when he booked the tickets, or was there either a routing, schedule, or some other kind of change? If there was no terminal change on the original ticket but AA changed it, there would have been a good chance to get some redress.

I think we're all wondering why someone would toss away thousands of dollars over a 20-minute bus ride - and there's likely a taxi available.

Especially in a case where RT fares are equal/less than OW, there's no real chance of a refund. In theory they could even try to re-fare to a OW fare! (Adding insult to injury.)