Andrew, I can share your frustration. Learning of material of possible value to your research and not gaining immediate access can be a downer. It may be a slim reed, but you might want to contact Dr. Lynda Crist of the Jefferson Davis Papers Project at Rice University to see what insight she might be able to provide. They made a broad sweep to locate JD-associated material, so their records may have some information that could help you get some sleep (or not!), and she is a very patient and considerate person. Good luck.