How did a 'Buy Now' button appear on my Google product listing without ads?

[hzl22]

one of the products I sell on shopify came up 1st page on google organic search and had a BUY NOW BOTTON, since I do not do google ads I wonder how did google put a BUY NOW BOTTON on my product. the product had the image and when you click on it there are a few bottons, one to go to website, the other to BUY IT NOW. my supplier called me super mad because she claimed I discounted her product intentionally and ran a google ad. The thing is I do not run google ads. Does anyone here ever got this buy botton without doing google ads?  my product on google did not have (sponsored) next to it, is that enough proof to give my supplier to show I did not do an ad? I read in another thread that google and shopify were doing something like putting buy bottons, has anyone heard about this?