If you ask me, I think you're just noticing short-term memory loss because you're looking for it now and have something to blame it on. I remember learning about this in a psych class...

Have you ever learned a new word or something and then all of a sudden you start to hear or read that word more often?

Everyone can relate man, pothead or otherwise. Everyone has walked into a room at one point and then said to themselves "why the fuck did i need to come in here??"

I think (for myself at least) its because I decide to go do something and then on the way there I start thinking about other shit and my body goes on auto pilot.