On Tuesday, Jeremy Irwin said he came home from working an overnight shift and found his daughter's crib empty, a window open and the family's three cell phones gone.
"The windows were open and lights were on and she was nowhere to be found," Irwin told "Good Morning America" Thursday. "We've been going over everything in our minds. We just don't have any idea."
Irwin said that his front door was unlocked when he returned home from work as an electrician at 4 a.m. to find his daughter missing.
Parents Questioned in Lisa's Disappearance
On Friday, Lisa's mother, Deborah Bradley, said that police accused her of having done something to her child.
"From the start when they've questioned me, once I couldn't fill in gaps, it turned into 'You did it, you did it,'" Deborah Bradley told "Good Morning America." "They took a picture down from the table and said, 'Look at your baby! And do what's right for her!' I kept saying I don't know ... I just sat there. I didn't even ask to leave. I just let them keep asking questions."
Bradley also said police accused her of failing a polygraph test. Police said they could not comment on this claim, but said Bradley is "free to say whatever she wants."
Garrett said such accusations may be an interrogation technique.
"One of the things you do when intervening in an interrogation is try to push people's buttons as much as possible because people who are guilty ... especially in a situation as emotional as a child being killed, either accidentally or otherwise ... [pressure can] push people over the edge ... and I think that's what they were trying to do," Garrett said. "Obviously they have some consideration that she was involved in this."
The parents told "GMA" they had not ended their cooperation with police
Irwin said that he only needed to take a break from the intensive questioning.
"We were in interrogated for a really long time Tuesday there again, answering questions. ... I just couldn't take it anymore," he said. "I told them I had to have a break -- no more questions today. I asked to be let go, and they let me go from police station. An hour later was when we saw the press conference from them."
Both parents denied on "GMA" that they had any involvement with their daughter's disappearance, and reiterated their willingness to cooperate.
Young welcomed any possible renewal of cooperation from the parents.
"If they say they're willing to continue speaking with detectives, I say great. Our door is open," Young told ABCNews.com. "Their involvement in the case is the best thing for this case. Our only goal is to find this little girl."
ABC News' Dan Harris, Michael S. James and Leezel Tanglao contributed to this report.