The man who murdered Libby Squire cancelled a meeting with the student's mother, claiming he is appealing his conviction and sentence.
Pawel Relowicz, 28, changed his mind about meeting Lisa Squire as part of a restorative justice programme.
Ms Squire, who was informed about the cancellation just over a week ago, told BBC Breakfast: "We can't find any evidence that (an appeal application) has happened so far.
"The police haven't heard anything, nor have the probation service or my restorative justice case worker - so I am not sure, really."
He raped her on a playing field before dumping her body in the River Hull in the early hours of 1 February 2019.
He was jailed in February 2021 for a minimum term of 27 years.
'I want to know how she died'
When she was asked why she wanted to question Relowicz, the Hull University student's mother told the BBC: "It's about being in the same space as the person who was last with her. In an ideal world, I would love him to tell me how she died because we don't know, and it's a question that does not leave me."
Saying she does not think he would say how she died, Ms Squire stated: "It is more for me about how she was feeling when she got into the car. Was she evidently warmer? Was she chatty? Was she quiet? Was she crying, or was she not crying? All those little questions that just eat away at me."
She added: "if I haven't done my absolute utmost to find out, then I just don't feel I am doing my job as a mother properly".
She intends to talk to officials in about six months to see if Relowicz will eventually meet her and believes it will happen because "I am not going to give up".
Ms Squire, from High Wycombe, Buckinghamshire, said the idea of him launching an appeal fills her with "dread" but she is confident there is no new evidence in the case.
She feels her daughter's killer is "backtracking" on talking to her ever since she agreed to the meeting, as he wanted to know which questions she would ask and also state which he would answer.
A history of non-contact sex crimes
Before he killed Libby Squire, Relowicz had a history of non-contact sex crimes including voyeurism.
Ms Squire feels it is her job to do as much as she can for her murdered daughter, which includes finding answers about how she died and also being prepared if her other children ask questions about it in the future.
She told the BBC: "I am never going to have the whole picture. By not seeing him at the moment, when I found out, I felt like I had let her down again.
"I felt like I had failed at seeing him."