"Phantom" LibreOffice icon appears

I didn't happen to be running in debug mode when this happened so I can't attach debug info just yet. Here's the version info:

[INFO 12:40:40.807534] [AbstractMain:176] Plank version: 0.2.0.660
[INFO 12:40:40.807656] [AbstractMain:177] Kernel version: 3.2.0-26-generic
[INFO 12:40:40.807752] [AbstractMain:178] GLib version: 2.32.3
[INFO 12:40:40.807823] [AbstractMain:179] GTK version: 3.4.2
[INFO 12:40:40.807894] [AbstractMain:180] Wnck version: 3.4.2
[INFO 12:40:40.807971] [AbstractMain:181] Cairo version: 1.10.2
[INFO 12:40:40.808049] [AbstractMain:182] Pango version: 1.30.0

The issue is that, occasionally after running LibreOffice, a "phantom" LibreOffice icon appears in Plank. You can see in the attached screenshot that it appears as running (with a dot near it) though when I right click the icon there are no windows to interact with. You can also see that it is NOT pinned to the dock.

Checking "pin to dock" and then unchecking it again makes the phantom icon disappear.

I'm running Xubuntu 12.04. DE is XFCE, of course, and WM is XFWM.