This Moon assumes a lot from the player, and requires you to go a bit out of your comfort zone when it comes to exploring.
The Deep Woods is a section of the Wooded Kingdom not found on its map, and must be entered by actually falling off the world at specific locations. Once there, you have to find a Coin Coffer -- which are invisible until approached -- that spawns near one of the seed-dispensing robots. Then it's just a matter of locating the little creek that runs through the area, and coughing up anywhere from 300-500 coins on the small plant growing between some fallen coins, until it gives you a Moon.
While I was able to find the Deeper Woods by myself the first time I visited the Wooded Kingdom, I was at a loss when it came to interacting with the sprout I saw growing in the creek.