Spanish Fail #3

My firm’s been cleaning house so my lunch breaks have been spent picking through the debris of industry for useful tidbits and today I got a quality paper box to hold my stuff.  While I was picking through things the janitor came by to add to the pile and as I stood there in my coat outside he grabbed my sturdy box and put it in the pile.  I lunged to grab it and prevent him from taking it but failed to properly state my sentiment:

“No, mi caja.”

I was a bit tired and thing I slurred “caja” into “casa”, so instead of saying, “no, my box”, I said “no, my house” which explained the puzzled look I got.