Confederate Money

[L Verge]

A bit off topic but perhaps as a point of interest; Longstreet in "Manassas to Appomattox" notes the following:

"Soon after General Lee's return ride (from meeting Grant) his chief of ordnance reported a large amount of United States currency in his possession. In doubt as to the proper disposition of the funds, General Lee sent the officer to ask my opinion. As it was not known or included in the conditions of capitulation, and was due and ten times more to the faithful troops, I suggested a pro-rata distribution of it. The officer afterwards brought three hundred dollars as my part." Longstreet goes on to say that he kept a hundred and gave the rest to men in Fields's division that were the most distant from their homes.

How did Lee's chief of ordnance "happen upon" such a large amount of U.S. funds?