I've missed my Pere Marquette connection a couple of times.
They've never held the PM but Amtrak made sure we got home.
Don't worry, they'll have reps available to make sure that everyone is taken care of.
Make sure that you make your presence known though, head directly to passenger services across from the ticket counters.
They won't come looking for you specifically so stay close and don't wander.
If possible, don't check any baggage so you can be ready to board whatever transportation they have available.
Last spring, the CZ was over 7 hours late and there were a lot of freaked out first time riders in my car - I was in coach that time.
One woman I spoke to had a lot of checked luggage and I looked for her but she was still waiting for her luggage.
They had one measly passenger van that held 7 passengers.
There were a few more people than that and they told those that didn't fit, to go back to passenger services to get vouchers - ugh.