I did see that in the documentation. I think I'm just a little confused haha.
This is what I'm clicking on in the tile map with result in top left:
gyazo.com/84661a73b6fa509e48305bb3f720cd19
I thought maybe it was because I have a HUD layer in front of the ground so it was selecting that. I tried moving the tilemap to the front layer and still get -1.
So is x/y supposed to be the specified coord of the Tile set/image or the coord of the mouse click? I had tried specifying x/y as 2/1 for the tile image as well as tried mouse.x/mouse.y and still got the same result.
Thank you all for the assistance.