Burger King’s “Whopper Detour,” which re-directed McDonald’s customers to the nearest Burger King to get a sandwich for only a penny, scored the Mobile Grand Prix at the Cannes Lions International Festival of Creativity, after winning the top honor in the Direct category on Wednesday.

The agency behind the stunt, FCB New York, rebooted the Burger King app to geofence all 14,000 McDonald's locations in the U.S. When Burger King app users came within 600 feet of a McDonald's, it offered them a Whopper for a penny, but only if they went to the rival restaurant to try to order it there first.

"You always want to be the original jury that finds something that hasn't won so far and, of course, as we walked out [of judging], we discovered it won the Direct Grand Prix which made us feel terribly unoriginal," says DDB Worldwide CCO Ari Weiss, who led the jury.

Of course, Weiss says the overlap is reflective of how pervasive mobile is today.

"For a direct campaign to be using mobile makes perfect sense," he says. "Mobile is everything today."

Weiss explains that the campaign was "mobile, mobile, mobile," which is why the jury members—almost all of whom had "Whopper Detour" in their top three list of entries—awarded it the Mobile Grand Prix.

"It drove app downloads, drove mobile commerce; it could not be more mobile," Weiss says. "It also proved that mobile can drive movement versus being secondary and the sheer audacity of posting it at 14,000 of its competitor’s stores couldn’t have been more on brand for Burger King."

Media efforts for "Whopper Detour" were handled by Horizon Media.