"The order to detach men from Morgan could well have been verbal. "
It may have been a verbal order, but I don't think so. That wasn't the nature of either Hindman or Holmes or for that matter of fact any higher level commander to NOT document such organizational orders.
After all just a very few years ago we did not know of the existance of Thomas Hindman's Copybook of Telegraphs which had been in a private collection until 1974. Even at that it has only recently, within the last 10 years, thanks to this board, come to the knowledge of more and more researchers, and has been a most important key in unlocking several mysteries regarding the reorganization of the Confederate Army in Arkansas in 1862. And has lead to several major reinterpretations of historical events and writtings and the locations of several misidentified sites.
Even with this revelation it is appearent that even these telegraphs are not complete. However, I doubt that Hindman's Copybook would have survived to this date had it not been in the hand of a newspaperman of the time that collected such correspondence and protected them.
Like the recent 100 additional volumes of supplements to the OR's who knows what else will turn up?