How Do I Not Remember Buying That???

Today while cleaning I came across DDR (Dance Dance Revolution) for the 360 (XBox) sitting at the top of one of our closets.  Since it's almost Christmas my thought process went something like this.  "Am I supposed to see this?"
"Wait, we don't have any money, how would John have bought this for me?"
"If he didn't buy it for me for Christmas, just how long have we owned this?!"
"Why can't I remember buying this???"
"Has this really been sitting at the top of the closet since we moved in?" (Which by the way was a year ago. Have I mentioned I am also not the most observant person?) 
I then found the game portion of it open and on the video game shelf (the dance pad was in the closet).  "Huh, apparently we have had it for awhile."

I told John he could have wrapped it up for Christmas and I would have never known.  Really though, how do I not remember having this?!?  When John traded in his original XBox and everything that went along with it, including my beloved DDR game (ok maybe I didn't play it as much as I should have, but still) I made a BIG deal about making sure he replaced it for me on his new (at that point) 360.  Which makes it even more baffling to me that I can't remember him buying this for me.  Like I know my memory isn't always the greatest (I blame hereditary for that), but really, why can't I remember this???  I am very excited that I stumbled upon this, now I just need to find some time to play.  I would have today during nap time, but I caught a cold from the boys and I feel like total crap.