A 60-year-old man presented with a suspected small intestinal tumor on positron-emission tomography-computed tomography. Small bowel capsule endoscopy (SBCE) was planned for close examination of the small intestine. To avoid retention of the SBCE due to strictures, a patency capsule (PC) was first used to evaluate patency. However, PC discharge was not visually confirmed during the 24-h period. No obvious PC was observed on plain abdominal radiography performed in the standing position. The patient underwent SBCE, assuming that the PC had been shed inconspicuously. SBCE revealed a neoplastic lesion with stenosis at a site thought to be the upper small intestine and remained stagnant at the same site for the duration of the battery. In addition, in the SBCE image, a PC shell was captured in the intestinal tract on the oral side of the stenosis. When the pre-SBCE plain abdominal radiograph was enlarged to confirm the details, PC was observed in the lateral and decubitus views as a dissolved shell only. To the best of our knowledge, no previous report has described the complete dissolution of a PC leaving only its shell during a 30-hour patency evaluation period. This case illustrates that, in the absence of visual confirmation of a PC discharge, PC may have remained in the body due to premature dissolution. Additional examinations or plain X-ray imaging should be performed to confirm this, with no preconceived notions that the PC will not dissolve within 30 hours of administration.