down on the cube farm, left then right then another left
That behavior is weird. You would expect it to work. Going on that premise ...
Are you sure that the trigger is firing? Have you put in debug so show that trigger is entered?
Is there any object on the canvas that can take focus? Usually this is more a behavior of trying to get a canvas to display than hide. I do not understand the behavior but I have found that creating a item that can get the focus and declaring is size 1X1 (ie so small that humans really do not see it) can make a stubborn canvas display. Maybe hiding is similar.
On a side note: If anybody has a different solution for making a canvas without a "focusable" item display I would love to hear it.