I will say that Dr. Ballard will come as close as anyone to knowing the specifics of this raid. I haven't talked to him in a while, but I have the volume from the Grant Papers that includes this time and I don't remember seeing anything about Houston. Actually, the Union soldiers, staff, and newspapers didn't say much about the Holly Springs Raid. They had to acknowledge that it happened, but it was an embarrassment that they more or less swept under the rug.
I'm thinking back to Grant's Memoirs, and he said something to the effect that...Van Dorn appeared at my secondary supply base at Holly Springs, Mississippi, capturing it. This showed the impracticality of moving a long line of supplies through an enemies territory, therefore I determined to abandon my campaign into the interior.
That's not an exact quote form the book, just a paraphrase, but it explains the point. I will say that it would be very unlikely that we will ever get conclusive evidence of the exact route from a Union source since they weren't with Van Dorn, and when it was over no Unionist cared what route they took. Grant has no significant reason to have known the route. It might turn up as trivia from an obscure Union document (letter, etc.) but more likely it will turn up from the Confederate side, if it exists at all.
I do know that there are still some German diaries and letters (CSA) from that campaign that are still in private hands that haven't been translated. Before you ask, some of the info needed to find them was lost in an email crash, but I think I remember enough leads to connect the dots again. Hopefully I can, and one day have access to the complete collection in a translated form. However, as I remember, this was infantry, and I'm not sure if any of the writers were in the cavalry or would have reason to know the specifics about the raid.
I'm not familiar with some of the names in this thread and would like to hear from any of you on anything pertaining to the MS CEN Railroad Campaign. I'll forward this link to my CW friends to see if anyone else had info I'm not aware of. Am also glad to hear about the upcoming article. If any of you are going to the Franklin, TN show December 3-4-5, please contact me.
Don