birth date 12/20/1929 Georgia (no city/town known)

I was always told that my fathers mother Evelyn Moseley Polk Wesley was my fathers birthmother, and that he was born out of wedlock. He was adopted by William Francis Polk sometime after 1935 when he married Evelyn Moseley I belive in Pasco County.

In a search of 1930 census records I found my grandmother listed as living in the household of her parents Dewitte Moseley in Plant City, FL, age 19 but no baby of approx 4 months was listed. This leads me to believe that perhaps
my father was not her birth child.

Any help would be appreciated. I have done a search for orphanages in GA but cannot seem to find them on the 1930 census.

Thanks!