When my dog Lulu went missing a few years ago, I was lucky to be quickly reunited with her, thanks to her ID tag and a pair of good Samaritans, but some pet owners aren't so fortunate.

A troubling new trend known as pet flipping — when someone finds, or in some cases steals, a pet and attempts to sell it — is on the rise across the nation.

Last year, more than 637 U.S. dogs were stolen, according to the American Kennel Club — a 4.5 percent increase from 2013.

The breeds most frequently stolen are pit bulls and pit bull mixes, followed by Yorkshire terriers, Chihuahuas, bulldogs, Pomeranians, Shih Tzus and German shepherds.

Craigslist ads often say the person can no longer afford to keep the pet, but the price tag indicates they want to make money more than they want to secure a good home.

Recovering a lost or stolen pet can be difficult, but you can take measures to protect pets and prevent pet flipping.

1. Don’t leave pets unattended — not even in your yard. New York pet owner Mary Ann Dineen paid $500 to recover her lost Maltese, which had been stolen from her front yard during a potty break. Occasionally, people see unattended animals as an invitation to steal, particularly if it is a popular breed or an unaltered dog. Dineen got her happy reunion with Corky, but only after canvassing the area with more than 1,000 fliers and acting on tips that led to the dog-nappers’ apartment.

“What makes this even worse, is that Corky had tags on the entire time,” she wrote in an article on About.com. “If these people were decent human beings, they would have returned Corky.”

bulldog with pink collar and id tag2. Make sure your pet has an ID tag at all times. Whether it’s a coffee run or a potty break in the back yard, don’t let pets leave home without their ID tags. Leashes wear out, pets slip through fences, and some dogs simply cannot resist chasing a squirrel or other distractions. An ID tag with updated contact information will be your first step towards recovery. Check your dog or cat’s tag to make sure the inscription is still legible and the phone number is correct. Adding an email address also helps.

3. Keep up-to-date photos and records. Many pet lovers have a few thousand pictures of their fur kids. In a previous column, pet detective Carl Washington shared tips such as selecting one picture to use on fliers. Rather than blanketing the community with thousands of posters, Washington also advises pet owners to focus on high-traffic areas such as neighborhood entrances and exits, nearby vet clinics and pet stores. Why the last example? If someone has stolen a dog, they may need to make a pit stop for supplies. Your flier could help jog an employee’s memory. If your pet is recovered, you also will need to prove ownership. In addition to photos, make sure vet records are readily available.

4. Don't share details about your dog with strangers. Don't answer questions about your dog's breeding, how much you paid for your pet or where you live. If a stranger asks you about breeding your pet, say it's been spayed or neutered — even if it hasn't. If the person seems suspicious keep a record of any identifying information.

5. Spread the word about missing pets. Be proactive about spreading the word. Post your pet’s info on free websites such as Craigslist and Lost Pet USA. Contact pet rescue organizations and shelters in neighboring counties. Ask friends and neighbors to join the search and amplify your reach through social media. Note any identifying marks and make it very difficult for anyone to flip your pet.

pet microchip6. Microchip your pet — and register your contact info. No bigger than a grain of rice, a microchip inserted under the pet’s skin serves as an added layer of protection (that's a microchip at right). Each chip has an ID that functions much like a Social Security number. If your pet is recovered, animal shelters or veterinary clinics use a scanner to detect the chip’s ID number. Armed with that number, they can look up contact information, but only if the chip has been registered.

“Folks may not understand that the chip only holds a number,” said Aimee Gilbreath, executive director of a Los Angeles-based nonprofit called Found Animals, which offers a free online microchip registry. “They think the code is like LoJack or GPS. It’s really important for folks to know that they have to register the chip in the first place — and keep contact info up to date — or the chip is useless.”

With updated contact info on file, Found Animals will email, call and send text message alerts up to four days after someone searches the registry. Gilbreath shared the story of a pet owner who had moved from California to Georgia and neglected to update her contact information. Fortunately, the email address had remained the same and an alert led to a happy reunion.

“People think it won’t happen to them,” Gilbreath said. “The pet is an indoor pet. It’s always with them, always on the leash. They don’t think about gardener leaving the door open or Hurricane Katrina. They think it won’t happen.”

Read more about how to keep all your pets safe from theft.

Editor's note: This article has been updated since it was originally published on July 24, 2013.

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Photos: (bulldog) Jane Holmes/Shutterstock, (microchip) Avid