Cathy,
The was a major battle at chester Station in May, 1864 but the fight of April 3, 1865 at Chester Station was one of many delaying actions during that time to allow the retreat of Lee's army. As to Milledge's men not being at the surrender, many units were either dispersed or captured as whole units by Federal forces during that time. Milledge's Battery was part of Nelson's Artillery Battalion of the 2nd Corps. The 2nd Corps artillery was in the Shenandoah Valley until March, 1865 when they were ordered to Richmond to rejoin the army. Nelson's Battalion was left in the Valley with Early's command while Carter's and Braxton's Battalions reported to Lee as ordered. Many of the 2nd Corps batteries have no record after this. The last recorded fight for Nelson's Battalion of which Milledge's Battery was a part, was Waynesboro, Virginia on March 2, 1865. The bulk of Early's forces were dispersed in this battle. Milledge's Battery was probably dispersed at Waynesboro and just disintegrated after this. This would account for none being present at the surrender. There were a lot of units carried on the surrender list which had no one present there. Records of some units are sketchy.
Len