Perhaps Captain Williams received a sick furlough or a furlough of indulgence, or was sent home to secure recruits. There may be evidence of such an order in his service file. Men sent home on leave in late 1864 and early 1865 had to pass around Sherman's army which was on the move during that time. Considering the state of confusion and ruin in the wake of Sherman's march, it's surprising that many made it home and back in time to be included in Lee's surrender.

I'd have to search his record to attempt a guess at this....