I took a quick peek at your website and see that you do not include the term “vanilla” in-text anywhere on the homepage, except once in the footer with tiny text at the bottom of the page. Nor is the term included in your page title. You have done little to optimize your web page for that term, Google is just respecting your choice to not optimize for that term.
I believe there are 2 issues with your question. I checked the data for the one example you provided and found no search volume, I