Police believe the girl -- who lost her left leg and hearing in a childhood battle with cancer -- is dead, but have not been able to locate her remains after weeks of extensive searching that focused on former homes of the Bakers, a nearby landfill, some mulch piles and a wood chipper. Investigators were able to locate the girl's prosthetic leg last week.
Adam Baker was taken into custody late last month on unrelated charges including assault with a deadly weapon, but is currently free on bond. When he returned to his Hickory home Tuesday, onlookers heckled him, exclaiming that he should be in jail, ABC News' Charlotte affiliate WSOC-TV reported.
Outside of Zahra's parents, who said they last saw her in bed the morning she was reported missing, authorities have only been able to find a single witness, a furniture store owner, who said they had seen the girl in more than a month before she vanished.
Hickory police said that early in the investigation Adam Baker was cooperating fully, but county officials remained suspicious of him.
Officials first became involved in the case on Oct. 9 when the Bakers reported a small fire in their back yard. It wasn't until later that day that they said they noticed their daughter was missing with her prosthetic leg, although her hearing aids had been left behind.
In a 911 call made by Adam Baker, he claims he saw Zahra in bed at 2:30 a.m. that morning. But in an interview with "GMA" two days later, Adam Baker said he hadn't seen the girl since early Thursday morning due to a hectic work schedule. In the same interview, he said that it was possible his wife, Elisa Baker, was involved in the girl's disappearance.
As the search dragged on, several neighbors and some family relatives came forward to claim Zahra Baker was repeatedly mentally and physically abused by her stepmother.
In one photograph from early August, obtained exclusively by ABC News, Zahra Baker is seen with what the photographer and family friend Brandy Stapleton said was a black eye. Stapleton said it was the last time she saw the girl.
Bobby Green, a former neighbor, told reporters early in the investigation that Zahra frequently had bruises but that Elisa Baker would always explain them away. "It's always she fell down, or she rolled out of bed or she didn't have her leg on right and couldn't walk right and fell. It's always Zahra's fault, for her injuries," Green said.
Brittany Bentley, a relative of Zahra's, told CBS News the girl "was beat almost every time I was over there for just the smallest things" by her stepmother.
The latest major break in the case came last week when police were able to locate Zahra's prosthetic leg in a brushy area a few miles from a former home of the Bakers. The discovery came just hours after police announced that Elisa Baker had been providing information to investigators.
Though police were aware Adam Baker had a warrant out for his arrest on unrelated charges, they did not take him into custudy until late last month because he had reportedly been cooperating with police.
ABC News' Yunji de Nies contributed to this report.