I could not find Beauregard's GO #45 either. Here are two references to check out. The first is a book about the battery itself that may shed some light on the subject. The second is a book on-line about Beauregard. Check out that time period (1863 - NOT 1862) and you will see that he was doing everything he could to get his hands on as many men as he could to defend the S.C. coast and Charleston. It could be that Hornsby assumed he would only be participating in the defense of Georgia and that Beauregard was ordering his unit, and presumably others, to S.C. This is, of course, only guess work and reading between the lines. Good luck in your research.