They do, it creates a 10 meter zone that removes invisibility from anything entering it lasting 1 turn/lvl. As it's so underutilized people may be under the impression that it works more like dispel, in that after it's cast it's over? I'm just guessing, but that could be causing some confusion. You don't have to see something cast it for them to have it active.
Anyway, if there are clerics around and your invisibility is going away, that's what is happening.