Was it an in-service passenger train? A freight train or out-of-service passenger train wouldn't show up.

Sadly, there's very little data available for most trains on US rails. For example, there's no way (AFAIK) to see what freight trains are active on the network. It's a little frustrating in comparison with how rich our air traffic sources are.

If anyone on HN knows of any richer sources for train network data, please let me know. I'm highly interested!