Mystery Has Been Solved

We have one of these guest bathrooms where when you open the door it will hit the door of the linen closet behind it if someone hasn't shut the linen closet properly.  Now, guess who is the only one in our family that ever opens the linen closet to put towels and sheets away.  Yep, me.  So, I've got a pretty good idea of when that linen closet door should be open had I forgotten to close it, which I don't!!  I hate going into that bathroom and slamming the door into that open linen closet door....Hate It!!  Therefore I am very careful about making sure it's closed when I leave. 
Now, for the past few months, yes months, this linen closet door has mysteriously been open from time to time  and I've been ramming into it. Cannot express the frustration!!!  Was it a loose door connection?  Was it the wind?  What could it be?
Today, Adam yells at me that we're out of toilet paper.  I go in and slam into that door again!!  As I'm pulling the new roll from under the sink, I'm expressing my questions aloud.  " Why is that door always open???"   Adam's response, as he's sitting on the potty, "I always check for monsters in there when I go to the potty."      Months!!!