"Sickness" was indeed often a result of an earlier gassing but then could also be a multitude of other things. The one you have found is the only Silver War Badge ASC man of that name so could well be him. His SS number indicates someone in the supply area who was a butcher, baker or a clerk. The only other clue is his medal card which has 4 Labour Company. As he was invalided out in 1916, these ASC Companies had not yet been absorbed into the Labour Corps but one can't be sure that it was the only one he went to war with. Another clue is that he went to France in October 1914 which says that he was either serving already or had served previously and was in the reserves.
Bad news is that there appears to be no war diary for 4 Labour Company - not unusual, they worked in places like on the docks and tended not to have unit diaries. Being gassed and working on the docks doesn't fit together so if it was gassing that invalided him out, then he must have changed units.
Gloomy I'm afraid but fairly typical lack of result with a man in a regiment/corps like the ASC who are much less well documented that the teeth arms.
MaxD.
