Fred Ramsdell was parked at a campground in Montana on Monday afternoon after camping and hiking across the Rocky Mountains when his wife, Laura O’Neill, suddenly started shouting.

He first thought that maybe she had seen a grizzly bear. Instead, Ms. O’Neill had regained cellular service and had seen a flood of text messages with the same news. “You just won the Nobel Prize!” she yelled.

“No, I didn’t,” said Dr. Ramsdell, whose phone had been on airplane mode, he recalled in an interview. But she said, “I have 200 text messages saying that you did!”

They had missed a 2 a.m. call from the Nobel committee that Dr. Ramsdell and two others had been awarded the 2025 prize for medicine for their research into the immune system. They also missed congratulations from their friends and family. His lab, Sonoma Biotherapeutics, said he “was living his best life and was off the grid on a preplanned hiking trip.”

Dr. Ramsdell, 64, had not expected any important phone calls that morning and was offline, as he usually is while on vacation. His wife, on the other hand, preferred to be more communicative with her friends and family.

“I certainly didn’t expect to win the Nobel Prize,” he said from a hotel in Montana. “It never crossed my mind.”