I had a similar experience in an Off-Licence staffed by a young Scot.
I was casually dressed [in kilt of course] so I was obviously not going to a weddding.
My Australian accent told him I wasn't a Scot. The pub was a frequent haunt of the expat Irish community so he came up with the on plausible explanation for this Australian in a kilt : off to a ceilidh are we? No, I replied I just like wearing a a kilt.
Probably trying to establish his credentials as a true Scot he said "I've got one of those". I replied "then you should wear it ".
I left leaving him rather puzzled looking.