Actually, there was a description of the couple - it just hasn't been played in this trial because it's not related to TPS' charges. There was a website set up that listed the physical description of the couple, including what they were wearing, and the woman's first name.
ETA: The couple in the park are described as (when detailing the handoff of Gabriel at the park):
"unknown Caucasian couple in their mid to late 30’s or early 40’s at Raymond Rimkus Park on Evers Rd. on December 27 at approximately 10:00 a.m. The male is described as husky, approximately 5’10” – 6’ and clean shaven, with dark brown or black hair. He was wearing a white polo shirt, and dark pants. The female is described as slender, approximately 5’6” with blonde hair that fell below the shoulder. She was wearing dark blue jeans and a red sweater."
