WO100/250 shows his rank as Trooper (as does WO127 and WO126, not sure why you thought he had been a Lance Corporal) the main roll shows his number as 3287, the supplementary actually show both numbers, although upon joining in Port Elizabeth the number 40562 was used.
I would say that he was merely given the former number actually upon being taken onto the strength of the 1st ILH after joining.
His medal appears to have been issued on the 20th of May 1903 and the Supplementary page of WO100/250, which confirms his South Africa 1902 clasp, suggests it went to the High Commissioner of Canada.
WO126/55-65 confirms he was a Canadian locomotive engineer from the United States.
Any appointment to Lance Rank was exactly that, an appointment only, moreover, a great deal can happen in a few weeks, those final closing weeks proved to be very brutal indeed.
The 1st ILH were formally disbanded on the 7th of July 1902 in Johannesburg, however, a new regiment with the same name was created in the Transvaal Volunteer Force after the war.