She disappeared more than three years ago. And in the public consciousness — in the maw of voracious news cycles — it sometimes seems as if she’s vanished for good.But not at home. Not where her mom and dad still hold a mournful vigil, where they hope against hope that their daughter, Evelin Valibayova, will somehow walk out of this black void and back into their lives.“Not a minute goes by when we do not think of our Evelin,’’ Artyom Valibayova, her father, told me Tuesday in an emotional interview via Skype from Azerbaijan. “The uncertainty of this kills us.’’“Our entire lives have been turned upside down,’’ said Nargiz Valibayova, her mom. “We pray every day that she is alive.’’At age 23, Valibayova brimmed with youthful promise three summers ago. She was a nanny on Martha’s Vineyard and later worked at a Cambridge restaurant, living in a Quincy apartment where she had a boyfriend and ambitions for a successful business career in America.We learned last month the identity of the man authorities believe is responsible for her disappearance and probable murder, a 52-year-old predator who was convicted of kidnapping a 9-year-old girl in 1986. According to court records, John D. Castonguay sexually and physically assaulted the girl and left her naked and bleeding in a gravel pit.We now know more about why Castonguay — released from federal prison in 2006 years before the wishes of the sentencing judge — is considered the leading suspect in Valibayova’s disappearance. We also know more about why he has not been charged in the case.For three years, court records about the investigation into Valibayova’s disappearance in mid-July 2011 have been locked away at Quincy District Court. At the Globe’s request, those records have now been unsealed and they outline statements made by Castonguay — some of them inconsistent and some contradicted by other accounts. And they detail conduct by him that is, in the words of one young woman to whom he acted inappropriately, “weird.’’Twenty-nine days after Valibayova was last seen exiting the North Quincy Red Line station, police interviewed Castonguay at his home in Quincy. At the time, he worked as a maintenance man at two apartment buildings, including the one where Valibayova lived on Hodges Avenue. Castonguay told police he had master keys to all the doors and apartments and said he was at Valibayova’s building on the day she was last seen.“He stated that he spent approximately thirty minutes at the Hodges Avenue apartment building sweeping and vacuuming,’’ the search warrant affidavit obtained by the Globe states.He told police that he had never seen or even met Valibayova.But when police interviewed Valibayova’s recent roommate, Dmitry Borkin, he told them a different story. “Borkin said Castonguay definitely met Valibayova a couple of times and had remarked to him that ‘I see you have a pretty new roommate.’ ”Borkin told authorities that he had received a text in early July from Valibayova in which she told him she had met the maintenance man.In one exchange with Borkin, Castonguay learned that Valibayova would be alone in the apartment by the middle of July. “Borkin said that he had told Castonguay that he was moving out of the apartment on July 13, 2011,’’ because he had taken a new job, the court record states. Four days later, Valibayova was gone.Without a body, the pursuit of murder charges against Castonguay is problematic. And authorities apparently were not aided by the execution of multiple search warrants. They searched two of his cars. They scoured his e-mail, cell phone, and computer records without obtaining evidence linking him to Valibayova’s disappearance.But in his application for a search warrant in late August 2011, State Trooper John Morris left no doubt about authorities’ suspicion.“I believe that it is probable that John Castonguay is involved in the death/disappearance of Evelin Valibayova,’’ Morris wrote. “By his own admission he places himself at the victim’s apartment building on the morning she is last heard from. He has access to the apartments via master keys and certainly has motive to remove her body since he is aware from his past crimes that there could be physical evidence linking him to the crime. I believe that he has the means to remove her body since anyone seeing the maintenance man removing a bag of trash from the apartment building would not be questioned. I also believe he would have the means and time to clean any blood stains from the surface area of the rug and wall.’’A couple of months before Valibayova’s disappearance, a young woman in a second apartment building maintained by Castonguay said she had been asked out by him. Castonguay describes himself in court records as married.The woman, who asked me not to use her name because she is frightened, said the fix-it man came to her Brooks Street apartment in Quincy to repair her door in the spring of 2011.She “said that Castonguay said that he knew she lived alone,’’ the court records state. “She said that Castonguay told her that he was single and did not have a girlfriend. [She] said that Castonguay asked if he could come over with a bottle of wine or take her out to dinner. [She] said that she had the feeling that Castonguay was watching her.’’When I spoke to the woman she said simply, “He was weird.’’He was also a rapacious predator, whose 2006 parole was revoked last November.When I told this woman that in 1986 he had lured a little girl walking her puppy to a remote area of Blackstone, where he brutally assaulted her, she was dumbfounded. “I have chills on my skin right now,’’ she said.My Skype interview Tuesday was interpreted by Katie Murashka, who worked with Valibayova on Martha’s Vineyard and has been trying to help authorities. It is not pleasant duty. Like Valibayova’s mom and dad, Murashka said precious days were lost in the immediate aftermath of the disappearance, when they said Quincy police downplayed the urgency of her case and told Valibayova’s friends “to stop watching so much TV.’’“Unfortunately, the [Quincy] police showed no due attention to Evelin’s disappearance,’’ Nargiz Valibayova said Tuesday. “The case was totally ignored and time was lost.’’Quincy police Chief Paul Keenan defended the early part of his department’s investigation. “We’re looking for the public’s help,’’ he said. “At this point, leads have dried up.’’Police and the Valibayova family want to hear from anyone who knows anything — no matter how trivial.A family 5,500 miles away wants to know what happened to their daughter. They are praying for some break. Anyone who can provide it is asked to call a tip line at 617-593-8840.Bakudaily.Az