Hi Phil,
I dont suppose his service history survived ? If so, would it show his NOK?
I dont know its this chap, just that he was 19th, and the J.Johnston is wearing a 19th cap badge, and I cant see any other Johnstons on the 19th as casualties.
My rationale is that he would not have had the 14/15 Star if he went abroad after changing units, and if he was killed in action he would not have been awarded the two victory medals, hence he shows up on cwgc but not on the medal rolls.
I accept theres lots of other variables, and not enough positive info, but like a challenge!
Regards
Pete
Ps Did you get the info from findmypast - he shows up on there but I dont have a subscription so dont know what info it gives.