The reference to that order [and the order itself] was taken from Capt Trigg's CSR's.
The date of S O #161 was Sept 20, 1863. The Alexander Papers regarding Arkansas end much earlier in 1863.
My previous post included the citation:
Fold 3
CSRs
Arkansas Miscellaneous
John T. Trigg
Capt. Trigg’s Btry Ark Lt Arty