The 27 March 1809 date is still interesting. Do you know your source for this date? After Peter's additional information below, I wonder if this is the date from the captured promotion list? I think Peter asks some interesting questions regarding the LH process in Foy's case. This whole process would make a wonderful article.
I hope you understand that my motivation was to move research forward, not a criticism of you. Again, I think the result of this thread shows the value of the Napoleon Fora. The whole is greater then the sum of its parts.