It doesn't look like a wildflower and may not even be from this mix

You are correct - it is a woody plant, with the specimen shown predating October. And if you are located in North America:

This aggressive grower poses a threat to native plants and communities. Its vigorous growth forms mats of monotypic evergreen groundcover that displaces and excludes most other plants, including native wildflowers. Extensive infestations can be found under forest canopies.

https://www.invasive.org/weedcd/pdfs/wow/common-periwinkle.pdf