A LATAM Chile Boeing 767-300, registration CC-BJA performing flight LA-5598 from Santiago to Santiago (Chile) with 2 crew only, performed a verification flight after maintenance and returned to Santiago for a safe landing. Chile's DGAC reported a part of an aircraft was found at the Mapocho golf course in Pudahuel (Chile) about one nautical mile south of runway 17R, however, no airplane yet reported the loss of the part. The part appeared to be an oil access panel. LATAM Chile reported one of their Boeing 767-300 (editorial note: CC-BJA) was performing a maintenance verification flight, an exterior panel fell off the aircraft into a depopulated area south of Santiago Airport onto a golf course. The airline is cooperating with the investigation.