You did not see anything, the Google search bar of your Pixel phone actually did a little flower animation for you.
To celebrate the spring equinox, Google has added a nice animation on the lower Google bar of Pixel phones, such as Pixel, Pixel 2 and Pixel 3. When you unlock your phone, you will see the animation of the flower with the green "G" logo for a few seconds before returning to Google's "Google" normal
Pretty. F * ck my allergies.