I suspect that Andrew was killed by a Yankee sharpshooter and most likely buried somewhat close to the rear of the siege line near their position.
It is also likely, that being in proximity to the city cemetery, he could have been transported there for burial.

The 43rd Mississippi Infantry were assigned to Hebrert's Brigade, Forney's Division at Vicksburg.

May 17.— This company left Chickasaw Bayou. Came inside the lines at Vicksburg and occupied the trenches in the rear of Vicksburg, from which place it remained until surrendered July 4.— Skirmishing commenced and continued all month. The first assault was on Tuesday, which was gallantly repulsed. May 22.— The second assault on Friday, all around the lines of entrenchments, was also repulsed.

Further down the siege line it was recorded:

06 11 1863 [Thursday]

"Some sharp shooting going on today. We are liable to be struck with a ball any minute. We are in a position where they fall all around us and in our midst. J. L. Miller [Co. B] was strick with one today. The ball wa 1s well spent and didn’t enter his flesh. It is said we have in Vicksburg, 31,380 men with 30 or 40 days rations.

"The hospitals begin to be filled up showing how much exposure, fatigue, hot weather, and short rations and wounds are diminishing our effective force. The indisposition is generally of a slight character and would probably soon be removed if we were out of the narrow limits to which we are confined. Hospital reports show about ten thousand under charge of the surgeons, one third of our force as I understand, though numbers after a few days rest improve, so back again to duty in the trenches."

Sometime after the surrender, a Federal Colonel had all the Confederate dead, re-interred in the City Cemetery, in an area subsequently titled Soldiers Rest, Cedar Hill Cemetery. There were some 3,000 so found and their graves numbered, marked with Cyprus head boards, and the list given to the ladies of Vicksburg. Over the years these Cyprus markers decayed and grave IDs lost.

Over the years, the list was lost. Sometime in the 1970's, approximately 2,000 men were identified and provided with VA Confederate tombstones. These were placed in rows in sections by state of organization. Later, in 1997 a list of some 77 East Tennessee soldiers was found by Jeff Giambrone at the Vicksburg Old City Court House.

Andrew is not found on any lists so far located. It is very possible his remains were placed in this cemetery.

Hebert's Brigade was stationed at Snyder's Bluff, and from Haynes' Bluff to the Mississippi, including Chickasaw Bluffs, when Grant's army landed below Vicksburg, and remained there until Pemberton returned across the Big Black from the battle of Baker's Creek, when, on the night of May 17-18, Hebert's men marched to Vicksburg and thence to take their place in the trenches east of the town, the right of the brigade across the Jackson road and the left in the main redan on the Graveyard road. They were just in time to meet the advance of the Union troops on the latter road, and on that road the artillery fire began that evening, May 18, which was continued every day with increasing severity until July 4. A heavy assault was made on May 22 and repulsed. On June 25, when the first mine was exploded under the works held by General Forney, "six men of the Forty-third Mississippi Regiment, who were in a shaft countermining at the time of the explosion, were buried and lost." The Forty-third was in the trenches next to this redan. The attempt of the enemy to occupy the breach was defeated. By this time the Federal works were advanced so close and elevated that the men of this brigade were obliged to work incessantly night and day repairing the parapets and constructing new lines. They were also exposed to the fire of a mortar on the Jackson road. July 1 another mine explosion destroyed the main redan near the Jackson road, but no attempt was made to storm. July 4th, in accordance with the terms of surrender, the brigade stacked arms in front of their line, and marched to bivouac in the rear of the works, where they were paroled. The brigade had 2,186 paroled; 219 had been killed, 455 wounded. The casualties of the Forty-third, Col. Richard Harrison commanding, were 25 killed, including Lieut. Marquis De Lafayette Hodo, and 33 wounded.

See also:

43rd Mississippi, "The Gentle Rebel: The Civil War Letters of 1st Lieutenant William H. Berryhill, Company D, 43rd Mississippi Volunteers," by William H. Berryhill, 170 page, paperback reprint costs $ 15.00.