Pisiform fractures like scaphoid fractures can be tricky to identify, and this is a good example of why! Even though I don't have a definitive yes/no answer, I wanted to answer this question as it is a good professional learning question for this site.
I agree that in this case, although the feature suggesting it might be artifact (the alignment of the line in comparison with neighboring trabeculae shadows), the position of the questionable cortical defect and length of the line suggests a possible hairline fracture.
But is this the only view? Usually hand XRays (especially when suspecting carpal fracture) are done with multiple views. It may require additional imaging, possibly even CT or MRI if additional XR remains inconclusive. Of course, clinical correlates will help guide you also - i.e. mechanism of injury and force of impact, age of injury, local swelling, bony tenderness, pain with motion, neurological or circulatory deficits, etc.
For we non-radiologists presented with such a case in the office, additional imaging views would be ordered, the radiologist's read would be reviewed, the radiologist may be contacted for clarification if needed, and/or an orthopedist may be engaged to review the case - plus a volar splint would likely be applied temporarily for stability (ulnar gutter may not allow sufficient room for swelling) until a definitive diagnosis and treatment plan can be determined.
Orthobullets is one of my fav ortho resources. UpToDate also has a good article on management if you have access.
As always, I am answering this with the assumption this is asked by a professional/student regarding an interesting case with the desire to learn and apply knowledge to future cases, not an individual patient seeking medical advice.