I’m far from an expert on the artillery, but I have been using the OR and sources like Wise’s The Long Arm of Lee to research Artilery units for a book that I’m working on about the fortifications at Centreville, Va.
The best that I can find on Maj. Francis W. Smith is that he was the former commander of the heavy artillery at Drewry’s Bluff in 1864, and that he was killed at Burkesville, Va. during the Appomattox Campaign, while serving with the 41st Virginia Regiment. Neither he, nor his battalion are listed as with the Confederate artillery in December, 1864. His battalion (Johnston, Neblett, Southside, and United artilleries) however, are shown on the May 1864 list.
According to Wise, the artillery was taking heavy losses during the last year. I would speculate that his battalion was consolidated into another. Several artillery companies also became infantry that late in the war, which might explain his presence in the 41st VA.
I may be telling you what you already know.