The only dumb question is the one you don't ask. I just checked my Shop Stats page and looked at my sold orders. I don't see a way to tell exactly how that person found me. I'm sure you know that your Stats page will tell you where your traffic is coming from (Etsy, direct traffic, Facebook, etc), so perhaps those shop owners see that their traffic increases from XYZ source and then their sales go up. It's reasonable to assume that the first thing led to the second. :)
If anybody has a more detailed answer, I'm all ears.