The Phys.org article New NASA radar technique finds lost lunar spacecraft describes the use of radar to relocate two spacecraft that were in orbit around the moon but who's orbit had not been actively tracked for a while.
Finding a derelict spacecraft at lunar distance that has not been tracked for years is tricky because the moon is riddled with mascons (regions with higher-than-average gravitational pull) that can dramatically affect a spacecraft's orbit over time, and even cause it to have crashed into the moon. JPL's orbital calculations indicated that Chandrayaan-1 is still circling some 124 miles (200 kilometers) above the lunar surface, but it was generally considered "lost."
This Wikipedia article suggests there are "frozen orbits" about the moon with inclinations of 27°, 50°, 76°, and 86°, but the LRO was inserted at about 90°.
Are low, polar lunar orbits in general relatively stable compared to lower inclination orbits, or is it still necessary to maintain station keeping capability? Do stable polar orbits actively avoid mascons, or does the mascon distribution somehow "average out" for polar orbits?