Are you using any ENB ? Anti-alias Asi or something that make it look better, i read many people having troubles like that when using ENB.
Also if it happens, don't close the game, just hit `
and type reloadscripts
It will remove it from the screen, it happened to me so many times but mine was resolution issues,
Use your recommended size, if you put bigger, the button may look there, but you have to find it clicking more to the right even out of sight were you can't reach, that may be your problem,
When I lower my resolutions, it looks good, but i can't click on it because is set to be on my optimal resolution. Hope it helps