Cannot remove Retrospect's retrorun file

I deleted Retrospect some time ago but have since discovered a "retrorun" file that the trash will not delete because it is "in use." I assume it's loading every time I start my computer and I would just like to get rid of it.

It doesn't show in startup items in account preferences so I can't "hide" it. And it's not in the library either (I guess because I moved it to trash). Any ideas?