Every year on the anniversary of the Sept. 11, 2001, terrorist attacks on America, Elizabeth Stringer Keefe attempts to connect with the owner of a wedding photograph found in the rubble at ground zero in New York. Thanks to the power of social media, the Massachusetts college professor ended her search after 13 years.

Keefe was given the photo by a friend in 2001. She found out Friday night the picture belonged to Fred Mahe, who formerly lived in New York and now resides in Colorado. Mahe worked in the World Trade Center in 2001, but wasn’t on the job when the planes struck the Twin Towers that Sept. 11.

“The picture was at my desk in the World Trade Center, Tower Two, on the 77th floor,” Mahe said in a Facebook message to Boston magazine. “The picture has been kept safe by [Keefe] for the last 13 years.”

The photo was taken at a friend’s wedding in Aspen, Colo. Mahe is posing in the far left of the picture.

Keefe, an assistant professor at Lesley University in Cambridge, Mass., told the magazine before Mahe got in touch with her that she calls attention to the photo on the anniversary of Sept. 11.

“I have always said to myself about the photo that I try not to think about what the story behind it is, and that I just want to get the photo back,” she said. “It’s a beautiful photo. There is a lot of happiness in it. There are tons of possibilities. And I think the thing that kept me committed to getting it back is that it was found regardless of what the story is.”

Reddit and Twitter helped spread word of the photo, which led Mahe to rediscover it. He said Keefe keeping the picture for 13 years was “amazing,” and he praised Keefe’s “dedication and persistence” in trying to find the picture’s owner. He said her determination conjured up thoughts of how people came together after Sept. 11 all those years ago, which he described as “the best of humanity,” according to Mashable.