Where is the code for my product page?
Some apps or Shopify tutorials require you to make changes to the product.liquid file in the theme. To prevent code duplication, the code for the product page is not in the layouts folder like other themes. The code for the product page in Pipeline is in the Snippets folder.
There are three different product.liquid files in Pipeline. The correct one to edit is in the Snippets folder.
If you need to modify the Add to Cart form for certain apps, you'll find that code in this file on earlier versions of Pipeline. If your theme is newer, as of Pipeline 4, the add to cart form has been moved to this file: