I suspect he was next to Blucher most of the time; Theodor doesn't seem like the sort of person who would "hide" with the baggage train, but I suspect he's aware enough of his personal importance to not risk his life like the Bishop or the Polish king.
Speaking of Casimir...
There is King Casimir. His cavalry are near useless in this fighting, but still he presents himself in blinding pageantry under the muzzle of Roman guns, deliberately drawing their fire down on him to lure it away from those making the actual attacks.
I'm no fan of the guy on a personal level but that's both really brave and kinda smart. Gotta give the devil his due here.