G'day. I had a chop at SGT Vantines's profile. Hope you don't mind. Regarding several queries in earlier replies, records indicate that he was captured on 29 April 1863 with many from his unit at Fairmont, VA, by Confederate cavalry under General William “Grumble” Jones and paroled the same day.
His MIA status occurred on the second day of the massive 2-week Battle of Cold Harbor (roughly 170,000 troops on both sides) where the bulk of the action that claimed some 17,332 lives occurred on the first four days. SGT Vantine and the 106th NY Infantry were in the 1st Brigade (COL Truex), 3rd Division (BG Ricketts), VI Corps (MG Horatio Wright). On 1 June, General Grant ordered the VI and XVIII Corps (MG William "Baldy" Smith) to relieve Phil Sheridan's Cavalry Corps which been engaged since the previous day, but the units were disorganized. The VI Corps (with Gideon) moved out after midnight on a 15-mile march while the XVIII Corps went to the wrong position and didn't support VI Corps, whose exhausted men arrived at the cavalry's front lines at 0900 and started digging in. Grant had envisaged an immediate attack, but Wright waited for Smith's troops to arrive, which wasn't until the afternoon. They set the attack for 1700. The delay allowed GEN Lee to reinforce the Confederate lines. The 106th was in COL Truex's 1st Brigade of BG Ricketts' 3rd Division, which was the ONLY Union Brigade to penetrate the Confederate lines in the attack; it briefly broke through but was pushed back. It is probably during this attack that SGT Vantine was killed along with thousands of others.
After another failed Union attack the next day, the battle settled into nine days of deadly trench warfare. A flag of truce to retrieve casualties was rejected by GEN Lee on 5 June, 4 days after the attack, but went ahead on 7 June. By then, few of the wounded were still alive.