I pulled up the schedules for passenger trains going thru Springfield, and I came up with the following trains passing thru there. All stop at Springfield:
Amtrak Texas Eagle (Trains #22 (northbound), #21 (southbound))
Amtrak Lincoln Services (Trains #301, 303, 305, 307 (All southbound), #300, 302, 304, and 306 (All northbound))
I assume you saw the train in the late afternoon, you would have probably seen either northbound Lincoln Service trains #304 or 306. They stop at Springfield at 4:56PM (#304) and 7:32PM. The only southbounds that stop in Springfield in the late afternoon are Lincoln Services #305 and 307, and they stop there at 8:39PM (#305) and 10:24PM (#307).