Intraoperatively retained foreign bodies are both medical and medico-legal problems. We report a patient who underwent a lower left lobectomy initially for nonresolving chronic organizing pneumonia. Rethoracotomy was performed due to a suspicious CT finding of a retained surgical sponge that turned out to be a GI anastomosis (GIA) staple line. Postoperatively, the situation was simulated using a surgical sponge adherent to the skin, to demonstrate the difference between the radioopaque marker of the surgical gauze and the GIA staple line. The facts of this case suggest the need for careful interpretation of such radiographic studies in the context of radioopaque materials intentionally employed during the first operation. If in doubt, digital magnification for more detailed and accurate inspection should be performed to avoid unnecessary rethoracotomy.