Joyce Finney, 77, of Darley Dale, was admitted to the hospital in a confused state on Sunday, January 11 and put on the Emergency Medical Unit.
Mrs Finney, who had lung cancer, sadly died the following day.
Her daughter Susan Finney, of Mansfield Road, Hasland, said: “On going through mum’s belongings we found that the money she had in her purse had gone.
“As far as I am concerned it is theft.
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“In my opinion someone has taken advantage of a very sick and confused woman.”
Mrs Finney also claimed her mother had been made to sign a disclaimer form – even though she could not read or understand anything at the time.
Three months after Mrs Finney complained, and following intervention from the Derbyshire Times, the hospital has finally apologised, admitted failings and promised to reimburse the lost money.
Lynn Andrews, director of nursing and patient care at Chesterfield Royal Hospital, said: “I would like to pass on our sincere condolences to Mrs Finney following her mother’s passing – and also to apologise that we’ve added to her distress.
“We did not follow the right procedures when Mrs Finney’s mother was admitted to hospital.
“Her belongings should have been stored safely as she was unable to look after them herself – and this did not happen.
“Our senior matron has called Mrs Finney, a formal letter of apology will be sent and the lost money will be reimbursed immediately.
“This event will be shared with our staff to make sure we learn from it. This experience is not what we’d want for any family member and we need to make sure it does not happen to anyone else.
“I am sorry that we have let her down by not responding to her complaint quickly and in person,” she added.
A hospital spokesman said it could not be established exactly how the money went missing.
They could not rule out theft.