How Did This Happen

There I am sewing in the bias binding trim on the Hawaiian dress.  Should be easy.  But its not because I run out of thread.....black thread. 

I search the house.  I have a lot of thread but nary a spool of black thread can be found.  I will not tell you the sheer number of different spools of blue and green thread I have on hand.  But no black and not a lot of white thread either.

Seriously, no black thread.  Really, how did this happen.  I know I sew a lot with black thread but really, no black thread.

Nope...so I am stalled until I can get some black thread.  Does this happen to anyone else?  Running out of a basic color of thread that should be on hand.