Originally Posted by GoAmtrak

The opposite can also occur. Inventory may say Sold Out, but due to mid-route turnover there could be space available the entire way by utilizing two different rooms. A good agent can sometimes help you cobble this together if you're determined to get a room and are willing to switch en route. Or, you could choose to ride in coach for one of the segments. (AFAIK, these scenarios are only possible for revenue fares, not on a single AGR award.)