This is the first reported case of a complication resulting from a lost kidney stone after a laparoscopic nephrectomy. The patient presented with a calcified right adnexal mass 3 years after having had a laparoscopic left nephrectomy for a staghorn calculus and hydronephrotic kidney. The mass was thought to be a rapidly growing teratoma and was excised. It proved to be a calcium oxalate stone. No similar cases could be found in the literature. Complications of lost gallstones after laparoscopic cholecystectomy are discussed.