It was a difficult operation for Agnes Ulmer at Vancouver General Hospital -- the 91-year-old grandmother lost her leg in a surgery to save her from a blood clot one month ago.

But she says she lost something far more valuable when a heartless thief masquerading as a cleaner pulled priceless family rings right off her hand over the weekend.

Now, Ulmer is pleading with anyone who knows anything about where three rings -- heirlooms destined for Ulmer's 6-year-old great-granddaughter -- might be now.

"Just bring back my ring," Ulmer told CTV News from her hospital bed. "You can have my leg. You've got it. I want my rings."

The man who stole it -- described by police as between 40 and 50 years old with light brown hair -- seemed to know his way around the hospital, and knew when to duck his head from being seen in hospital surveillance footage.

And in his visit to her eighth-floor room Saturday at about noon, he also knew enough about Ulmer to know she had rings and where to find them, Ulmer said.

"He seemed decent," recalled Ulmer. "He said, my wife is cleaning rings. Would you be interested? He was so polite, he dressed like an ordinary person."

The man took the rings from her hand, she said, and walked away. He never returned.

Ulmer is beside herself, because she feels guilty about giving away the rings, including a wedding band that reminded her of a life-long marriage with her husband who recently passed away, said her grandson Jason Dudlets.

"It's not the value of the ring we're worried about, it's what the ring represents," he told reporters Tuesday morning.

"It represents everything that's good and some scum just walked into this hospital and took it from her and robbed her," he said.

Agnes Dudlets said she thinks the man knew the building because he knew where to go -- and because no one stopped him.

"The only thing that's left there is grandma, who sits there and cries all the time and she sees the scars on her fingers from the wedding bands," she said.

A spokeswoman from Vancouver Coastal Health said that even though three rings were stolen -- one platinum and two gold rings -- that is not cause to blame the hospital security.

"To have only one reported theft is proof that those kinds of measures are adequate," said Vivianna Zannocco.

But Health Minister George Abbott called the thief the "lowest form of human life" after a press conference in Victoria.

He said he is proud that hospitals are open places for relatives and friends to visit sick people. But now he says hospital security systems have to be re-examined.

"The consequences of being open are that we have jerks and lowlifes who take advantage of us," he said Tuesday.

Police are asking anyone who has seen these rings or the man who stole them to give them any information they have.

Police described the man as white, about five feet, nine inches tall, and between 40 and 50 years old. He has brown hair and was wearing white sneakers, a baseball hat, and possibly a parka coat.