Quest description:
''Directly east of Auberdine lay many moonkin caves. The one closest to Auberdine has a Moonkin Stone inside it. Lunaclaw, the defender of the stone, will face you only when Cenarion Moondust is applied to it. Lunaclaw possesses within it a strength that you must use as one of the Claw.''
There are a lot of caves on that zone, you surely entered in one without the moonkin stone.
The one it got it is the nearest to Auberdine, as the quest says. To be more exact, i would say is the closest to the village on the east, but the one on the north
I am in the right cave and there is no Moonkin stone, you can check it for yourself. Also did this quest before, so i know the cave where it should be.