Anne Wills, the founder of Dogs Finding Dogs, works with her shepherd-lab mix, Heidi, to find a lost cat in Hampden. (Barbara Haddock Taylor/Baltimore Sun video)

As she struggled to unload groceries from the back of her car, Sherrie Schenning got an uncharacteristically queasy feeling.

Her family's Essex neighborhood had always felt safe, but on this recent Saturday, she noticed two unfamiliar young men in a nearby schoolyard eyeing their home.

"They looked like they wanted to steal something, but there was nothing valuable in the yard," she says — just her shopping bags and the family's beloved 12-year-old dog, Bella, who was snuffling around for attention.

Five minutes later, the groceries were put away, the young men were nowhere in sight, and Bella, a floppy-eared Yorkshire terrier, was gone, an apparent victim of what some are calling an increasing crime problem in the Baltimore area: dognapping.

"With the economy the way it is, a lot of people are in a bad way, and we're seeing more dogs get stolen for all kinds of reasons," says Anne Wills, who runs a nonprofit in Arbutus that uses trained search dogs to locate missing pets.

The American Kennel Club, which maintains a national database of dog thefts, says its sees a nationwide trend. The New York-based group reports that the number of reported thefts more than doubled between 2009 and 2011, rising from 162 to 432 over those years.

"And those numbers are just scratching the surface," says Lisa Peterson, an AKC spokeswoman. The organization bases its figures on media reports of stolen dogs and customers who call its Companion Animal Recovery service.

Wills says animal thieves have many motivations. Many steal dogs to sell, ransom, breed or give away. Individuals tied to dog fighting are always on the lookout for large, muscular canines they can train for bouts — or weaker ones as "bait" on which the fighters can learn to maim or kill.

"These people want to keep their fighting dogs in shape and they're looking to grab little dogs that can't fight back," says Darlene Harris, the former manager of the Baltimore City shelter. "It's horrific."

The perpetrators sometimes dump the bait dogs, or return them, scarred or missing appendages, Harris says, adding that the Baltimore Animal Rescue and Care Shelter has gotten several such dropoffs a week since 2010.

City and county police say they've noticed no significant spike in dog thefts, but Wills and Harris both say they've seen a surge in the Baltimore area over the past year.

"It has definitely gotten a hell of a lot worse," Wills says.

Her organization, Dogs Finding Dogs, gets about 15 calls a day and works a dozen or so cases at a time. More than half now turn out to involve acts of animal thievery.

Chelsea McKenzie, a pit bull owner from Glen Burnie, has lost two dogs to thieves.

"It's the people [involved] who are the animals," she says.

The dog advocates who track thefts say perpetrators often travel away from their own neighborhoods to scout for victims and spend time casing scenes or cultivating dogs before they act.

In one recent case, two young men from South Baltimore traveled to Patapsco Valley State Park, where they snatched an Ellicott City man's dog when he left it off its leash during a walk.

Wills' team tracked it from there to Dundalk, then later to Brooklyn, where police had to be called to help her retrieve it from individuals who cursed and shouted threats.

Peterson, of the American Kennel Club, has heard of thieves stealing dogs from cars, off leashes in front of restaurants, even from animal shelters.

Wills says owners should take precautions, including keeping pets leashed when outside; never letting them wander unsupervised, even briefly; and getting them microchipped for easy identification,