Don't know who Collins is, and with regard to the Campbell mystery, the information I had seemed to suggest a proper time differential in the communications to make Maj. Cabell a candidate as a quartermaster officer before he became a Brig. General. As I said, many reason why not.
Have you looked at Glen Ely's article in the current (April, 2007) issue of the SWHQ? It is a very interesting snapshot of issues that confronted Texas on the frontier during the War, especially driling in on cattle sales to both sides. His research and sources might help answer some of your questions.