That's actually a pretty normal artefact of computational photography on modern smartphones. The giveaway is that, where the mast should be, there are two faintly-visible vertical lines. If you look clearly, you can see an identical spacing of vertical lines up the sail where there should be a shadow of the mast, yet only a single masthead. And, if you look around the photo, you will see several examples of vertical lines with identical spacing.
Most phone cameras now use computational photography, which involves capturing a burst of images in rapid succession, then digitally combining them to enhance clarity, reduce noise, and compensate for motion.
In this case, the mast of the smaller boat appears to be missing, with only a couple of faint lines in its place. A likely explanation is that the mast was too thin or faint to be reliably captured across the entire frame sequence - especially if:
- The mast blended visually with the background (which it does).
- The boat and/or camera was in motion during capture (likely both were)
- The image was taken at some distance (which it was, as evidenced by some other indicators)
- Lighting was low or inconsistent (I don't think this was the case)
- The phone's algorithms prioritized background stability over transient, low-contrast features
During frame blending, objects that don't appear consistently across frames - especially thin, low-contrast ones - are often treated as noise or ghosting artifacts. The algorithm then suppresses them, effectively blending them out and reconstructing the background instead. This process can create a faint blur or "ghost" where the object partially existed.