Well lunar gravity varies a huge amount by location, it may be possible for some of it to somehow end up in actual orbits, especially when it's intentionally done so.
My understanding was that those variations in gravity ("mascons") rendered stable lunar orbits next to impossible. On Apollo missions, orbits degraded by many kilometers over the course of just a few days.
Interestingly, a researcher looking for probable impact sites found Apollo 11's ascent module could potentially still be in orbit. (Though, it's probably not.)
