'Hi Mom God Bless': Mystery message cheers Chicago hospital patients

In snow on the parking deck rooftop of Chicago's Rush University Medical Center, someone wrote a message in large letters visible to patients.

It's a medical mystery of a different kind. One that warms the hearts of those who most need it.

In the snow that piled on the parking deck rooftop of Chicago's Rush University Medical Center, someone wrote in large, clean letters: "HI MOM GOD BLESS" (with a smiley face for the 'O," for good measure.)

No one knows who did it -- or why.

But the message has brightened the bleak hours of many, according to Angela Washek, a nurse in the hospital's intensive care unit.

It appeared early Sunday morning, after Washek saw a group of men running around on top of the parking garage.

"I didn't know what they were doing," Washek said.

She took a closer look when a patient's daughter stood at the window of room 1155, and began to cry. Her mother had yet to wake up from surgery.

That's when Washek realized it was more than a group of men playing around on top of a parking garage.

"My patient's daughter wished she could have done something like that for her mother," Washek said.

The incident was first reported by CNN affiliate WGN.

Although the recipient and the sender are both a mystery, the cheer spread beyond just one person. The message could be seen from about 70 to 80 hospital rooms, across four different floors covering the surgical, intensive care and oncology units.

Deb Song, a hospital spokeswoman, said the simple message inspired patients and doctors alike.

"We are trying to find out who put the message up there because it has made so many staff and patients smile," she said.

The gesture is now covered by parked cars, but the sentiment of the message lingers.

"It reminds us," Washek said, "to fight for their families, as well as our patients."