Most ovarian cysts are physiologic (normal) and are seen on ultrasound.
Surgery for these are not indicated unless >6 cm (they can twist), have malignant features (thick walls, nodes, septations, etc), or if they persist at the site of pain. It's possible your cyst was this type of functional cyst & regressed on it's own. Ultrasound can be used to follow these prior to surgery. Good luck.