Maybe my phone case making a pinhole for light somehow?
Your camera lens is made of several pieces of glass. The glass is designed to admit as much light as possible on to the sensor, but at each layer, a small amount is reflected.
If the source light is bright enough, especially in comparison to the background, these reflections bounce around a bunch and eventually hit the sensor. Normally, any reflections are very faint and get washed out by the rest of the image, but the sun is like 1000x brighter than the sky, so even a weak reflection shows up.
