It turns out it was D801-23 going to Sawyer to pick up last night's D700 and bring it to Grand Rapids.
Here are the light engines in Riverside.
This was around 3:28 pm this afternoon.
I then drove to St. Joseph and waited, and waited.
Finally, around 5:25 pm, I caught D801 crossing the St. Joseph River in St. Joseph with D700 in tow.
These photos were taken from the West Basin Marina. There were some cars parked there, but I pretty much had the place to myself. It sounded like everyone was over at the Yacht Club, hopefully not spreading the Rona.