I was very lucky to see the Amtrak train, but there were some real train enthusiasts at the loop pullover site waiting, and they told me it was coming so I waited a few minutes extra. Can't remember the reason it was on the track that day, but it may have been track maintenance. Click on the link I posted to the loop and you will see the Amtrak train. Could also have been fires.
Sorry, you missed the trains, Arch. They have been constant any time I stop there. Now, if you REALLY want to experience trains, try staying in Mohave Narrows Regional Park in Victorville, CA. There is a very busy track that borders the campground, and then behind it, there is another single track. Get one of the pull-thru spots on the west side of the campground, and you will literally have trains blowing their whistles in your backyard--all day and all night! One tip, however. When they say they lock the gates at dusk, they really mean it. I had to walk a couple thousand feet in the cold and dark to get the code to get in, only to discover the lock was not really completely shut! Kind woman drove me back to my vehicle so I could get in.