I agree with that, and my wife was the one who confirmed it. I'd
had two girls in my life who rummaged through my pencil cases.
And...well...they were actually very "not automatic". The first one
did it when I was already in a steady relationship with my wife,
and the second one did it when I was already married for 3 years
(for goodness sake!).
Ask any girl, and she'd probably tell you it's a way of telling the
guy that they're *very* comfortable around with them. May or may
not mean they took a fancy to you, that's what I feel, but my wife
believes the chances are high it is so...