I would have felt uncomfortable, as well. I used to be a teacher and was grateful when parents or the community contributed to my students' learning experiences. If I'd been the teacher I would have asked if I could show the class your needle set and explain how it worked. And even if the shop can't sell KP items, there are other needle sets they could sell, I'm sure. If the owner chooses not to carry such an useful item...
what is that to you? As far as the sales of the shop goes, it seems like a happier, bonded class would speak for itself, reputation-wise.
I don't know. People are weird. And it seems like the older I get, the more I have to struggle to not
get angry when stupid things like that happen.