I can confirm that after reviewing your story stats very carefully, none of your writing has been Boosted.

If a story has been Boosted, you will receive an email and clearly see the Boost indication on your story stats page. I'm going to work with our user services team to see if we can make that more clear (and show an example) in our documentation here: https://help.medium.com/hc/en-us/articles/215108608-Your-stats#h_01HHMPGQFDFQC1GVV40QY5N33G

If you're just seeing a peak in your stats, then that's just our distribution algorithm doing what it does -- and doing it well! Stories do NOT have to get Boosted to get distributed, see a spike, or get high traffic. So when you see that a post has done well, that's not necessarily an indication of Boost.

I wrote on the Medium blog last year (https://blog.medium.com/a-nosy-faq-about-nominating-stories-for-our-boost-44bbf79549c) about how five times as many non-Boosted stories get high traffic every month than Boosted stories on Medium... and we love to see it! Some writers like to claim that it's "boost or bust" and stories like yours show clear that it's simply not the case.