My practice is to put out the ten pieces, but not because of any sort 
of chashash regarding the bracha. Rather, I find that they cause my 
bedikah to be somewhat more careful and thorough. There have been 
years when I missed one or two, and I keep on looking until I find 
them.

Regarding the fears of never finding the missing piece: The chometz 
is placed around the house by someone other than me, and they write 
down a list of where they are all placed, so that even if I give up 
looking for it, we'll still be able to retrieve it and get rid of it.

IIRC, one year they deliberately put out only nine pieces, just to 
keep me alert and looking. I thoroughly complimented them on that 
idea.

Akiva Miller