Because of the nature of this negotiation, I have little doubt detailed records were kept, most likely with sworn affidavits involved. Those records are probably housed in the National Archives, but that is just a guess. Figure out where they are located and you will probably have many questions answered.
Biography of Colonel Richard H. Musser
History of Howard and Chariton Counties, Missouri
"...In 1865, the war being over, Colonel Musser
located in St. Louis and engaged in the practice of law. There he continued the practice with distinguished success for some twelve years. Among other important cases in which he was interested as an attorney were several before the international joint commission sitting at Washington, D. C., against the Republic of Mexico for damages for the murder of General Parsons, Colonel Standish and Colonel Conrow. He managed these cases with so much tact and ability that he recovered judgment amounting to over $143,000 in gold."