Provost Marshal Records starting at page 832 0n reel f01658, show Robert Highley, Thomas Gaines and Mrs. Amelia Hall were reported heading for California, via New York, on a steamer supposedly leaving June 1, 1865. It gives physical descriptions for all three people. These are the records on the Missouri Secretary of State website.
I realize you are looking for information on John, but thought this might be of interest.