On the Military Hospital Admissions and Discharge Registers there is a Second Lieutenant J H Corbett, 2/3 Battalion London Regiment, aged 32, admitted 2/6/1917, ailment Pyrexia of unknown origin. Could this be him?
Added- found a John Hampton Corbett, 22037, Corporal Canadian Infantry,then 2nd Lieutenant Imperial Forces also 2nd Lieutenant London Regiment, could be your man?