I have been having this issue as well.

I am using a keyboard/mouse set up so I do not have the crosshot bar, however it always shows up on my #9 hotbar, which is set to visible, and always appears in the 4 slot. It shows up exactly were I have it set on many of DOH jobs and has showed up randomly on more than one of DoW/M class hotbars over the past couple of days. Often after a battle or instance.