What are the chances that a US army solider stationed in London, England in the spring of 1944, could be found, in order to help identify health and medical issues of a child born in 1945?

The birth father never knew about the girlfriend being pregnant. He was shipped back to the states and the birth mother found out afterwards she was pregnant.

The child was given up for adoption and does not want to make contact with the birth father, just looking for medical history information.