I think I found out what happened to my missing hen.
My cousin got off work a little earlier than normal today, September 23, 2013. After he got home my cousin took his dog for a walk, rounded the corner of a tree line, and just happened to see a chicken hawk on top of one of my Rhode Island Reds.
The dog took off after the chicken hawk, which let the chicken go and flew to safety.
My cousin said the chicken jumped up and limped off. Hopefully it was not injured to bad. I looked at my 4 Rhode Island Reds and did not see any blood on them.
When the hen was attacked it was out free ranging and in the chicken yard.
After this incident I am considering covering the chicken yard with monofilament fishing line in series of grids. But, I want my chickens to be able to free range.
Another option is to stick with large breeds of chickens and to get a couple of roosters. My wife wants some Buff Orpingtons, and I want some Dominiques, aka Dominicker. When we get the new chickens we will probably get at least one rooster of each breed, then another rooster for the original dozen chickens. This will give us 3 dozen hens and 3 roosters.
The chicken who came up missing was a rather small Speckled Sussex. This was a very tame chicken, which might have contributed to its undoing. Rather that running from danger, maybe the Rhode Island Red and Speckled Sussex just stood there looking at the hawk.