On her second day of testimony at the trial of Brian David Mitchell, Smart told of an encounter with a homicide detective at a downtown library in August 2002, The Salt Lake Tribune reported.
Smart said she was robed and wearing a veil when the detective introduced himself to her and Mitchell's wife, Wanda Eileen Barzee, and said he was looking for Elizabeth Smart.
The detective asked Smart to remove her veil but Smart said Mitchell stepped in, saying he was her father and that she couldn't remove the veil for religious reasons.
The detective finally left and Smart, who was 14 years old at the time, remained captive for seven more months.
"I felt like hope was walking out the door," Smart said Tuesday. "I was mad at myself that I didn't say anything. I was mad at myself for not taking the chance ... I felt terrible."
Smart testified earlier that Mitchell threatened to kill her and her family if she tried to escape.
She called Mitchell a manipulator who used religion to control people.
Mitchell watched Tuesday's proceedings by video from an adjacent courtroom because he refused to quit singing, the Tribune reported.