Nadia Popovici kept shifting her eyes from the hockey game to the back of Brian Hamilton’s neck.

Mr. Hamilton, an assistant equipment manager for the Vancouver Canucks, had a small mole there. It measured about two centimeters and was irregularly shaped and red-brown in color — possible characteristics of a cancerous mole, signs that Ms. Popovici had learned to spot while volunteering at hospitals as a nursing assistant.

Maybe he already knew? But if so, why was the mole still there? She concluded that Mr. Hamilton did not know.

“I need to tell him,” Ms. Popovici, 22, told her parents at the Oct. 23 N.H.L. game between the Canucks and the Seattle Kraken at the Climate Pledge Arena in Seattle.

Ms. Popovici typed a message on her phone and waited for the game to end. After waving several times, she finally drew Mr. Hamilton’s attention, and placed her phone against the plexiglass.

“The mole on the back of your neck is possibly cancerous. Please go see a doctor!” the message read, with the words “mole,” “cancer” and “doctor” colored bright red.

Mr. Hamilton said he looked at the message, rubbed the back of his neck and kept walking, thinking, “Well, that’s weird.”

Ms. Popovici said she regretted the message and thought at the time, “Maybe that was inappropriate of me to bring up.”

After the game, Mr. Hamilton went home and asked his partner if she could spot the mole. She could. He asked the team doctor if it was worrisome. It was. Then after he had it removed, he waited for the biopsy results to see if the fan sitting behind the team’s bench had been right.

Indeed, Ms. Popovici was correct, and she had just saved his life.

“She took me out of a slow fire,” Mr. Hamilton said at a news conference on Saturday, his voice quavering at times. “And the words out of the doctor’s mouth were if I ignored that for four to five years, I wouldn’t be here.”

Specifically, doctors later told him, it was type-2 malignant melanoma, a type of skin cancer that, because it was detected early, could be easily removed and treated.

“With melanoma, just like many other cancers, the success of the treatment or the cure is often dependent on the stage of disease — and the sooner you find something, the better it is,” said Dr. Ashwani Rajput, the director of the Johns Hopkins Kimmel Cancer Center.

Mr. Hamilton recalled the doctor telling him, “I’m going to diagnose you with cancer and I’m going to cure you of cancer in the same phone call.”

Once he knew he was fine, Mr. Hamilton asked the Canucks franchise to help him find the woman he described as “a hero.”

Mr. Hamilton wrote a letter that was posted on the team’s Twitter account on Saturday that said: “To this woman I am trying to find, you changed my life, and now I want to find you to say THANK YOU SO VERY MUCH! Problem is, I don’t know who you are or where you are from.”

It took less than three hours to find Ms. Popovici, who had been sleeping at her home in Tacoma, Wash., that afternoon after working overnight as a crisis intervention specialist at a suicide prevention hotline.

She woke up to texts and missed calls from her mother, Yukyung Nelson. “I think she was just shocked,” Ms. Nelson said.

Ms. Popovici, who had already planned to attend the game on Saturday between the Canucks and Kraken in Seattle, was invited by both teams to meet Mr. Hamilton.

He had just finished a news conference about what had happened. Referring to Ms. Popovici, he told reporters, “My mom wants her to know that she loves her.”

Later that afternoon, he repeated the message to Ms. Popovici in person.

“It was the sweetest thing when you were talking about your mom,” she told him as they met properly for the first time.

At the game, both teams presented Ms. Popovici a combined $10,000 scholarship to use for medical school expenses.

“Some people are saying this is not even going to be a drop in the bucket, but trust me, it feels like everything,” she said. “I’m really just so grateful.”

She watched the game from the same seat where she had spotted the mole. Everything, she thought, had gone right that day: A future medical student had been sitting close enough to a team bench where an assistant equipment manager was, thankfully, not wearing a jacket large enough to cover the cancerous mole on his neck.

“This entire experience has been so rare,” Ms. Popovici said. “And I will just cherish it.”