One Missing Piece

I used to be complete,
all whole and put together
A head, both hands, two feet
and a heart as tough as leather
But one day without warning
I lost a little bit
and now I am in mourning
for the want and lack of it
I search high and low and in and out
and never can I find
that bit which I am now without
I may just lose my mind
I try to call to no avail
It never seems to hear
My searches always seem to fail
The piece is just not here
So I still look whole, you'd never know
Two feet, both hands, a head
All the parts where parts should go
But still a sense of dread
Its not even something that I need
and I'd survive just fine without it
Its causes pain, I can concede
and I don't know much about it
I had it once, it made me grin
But it also made me weep
It made me ache and pine and spin
It tore apart my sleep
But still I cannot let it go
without it, I feel bare
I wish I didn't want it so
I wish I didn't care
Keep looking though I face defeat
Partial person without peace
I'm lost, morose, and incomplete
for one tiny missing piece