Randomly "appearing" Moonkin Form button

[Tradu]

I just updated my UI(added/changed addons, slightly altered the layout). I did LFR to test it, and sometimes an invisible Moonkin Form button appeared(as in, randomly spawned into existance and went away just as randomly) in the area marked with red on the image linked below. Does anybody have any ideas what it could be? I've checked all my Bartender4 bars, and none of them are in the area that is affected.
The main reason the button is being a pain is because it appears in one of the areas I have to click very often to change targets for multiDoTing etc.

My new UI

EDIT: More precise location. And apparently its always there(still no Bartender4 bars anywhere near that area)

[Deleted]

Type /fstack and hover over the area; that should hopefully tell you the name of the addon in question.

[Tradu]

Okay, so apparently the button was on Bartender Bar 9, which wasn't even being displayed. Thanks for the help, problem solved.