In New Jersey.
"The artwork appears to be unharmed, said Les Wiser, special agent in charge of the Newark FBI office. The FBI said extensive media coverage of the theft led to tips that enabled the agency to recover the painting. But the agency did not reveal when, where or how the painting was recovered, citing an ongoing investigation."
UPDATE: The New York Times has more. Looks like David Nishimura was on the money:
"Contrary to earlier law enforcement theories that the theft was carried out by insiders, they did say it appeared that the thieves probably had no idea what kind of art-historical loot they had stumbled upon when they broke into the truck overnight in a parking lot at a Howard Johnson Inn near Bartonsville, Pa. 'This time of year, close to Christmas, they probably thought they’d found a truck filled with PlayStations and broke in and started looking for the biggest-looking box,' said Steve Siegel, an F.B.I. agent who serves as the spokesman for the bureau’s Newark office. 'Basically, it’s a target-of-opportunity typical New Jersey cargo theft. There are literally predators — for lack of a better word — who when they see a tractor-trailer or a cargo vehicle parked for any length of time start snooping around.'”