I suspect they were re-interned at Little Rock
Little Rock National Cemetery
Little Rock, Arkansas
Little Rock National Cemetery in Little Rock, Arkansas, opened in 1866, when the Federal Government purchased land from the city cemetery to relocate the remains of Union soldiers from across the state to a more central location. Many of the first burials were reinterments from Pine Bluff, DeVall’s Bluff, Lewisburg, Princeton, and Marks' Mill, among others. Two years later, in 1868, the site was officially established as a national cemetery
https://www.nps.gov/nr/travel/national_cemeteries/Arkansas/Little_Rock_National_Cemetery.html