The customer could be someone you know. He might have visited your store before. He may be neat and well-mannered. Then he asks to see two watches, to “compare them in better light.” And once he gets his hands on them, he bolts for the door.

It’s called a “grab and run”—and so far this year, it’s occurred once a day on average, according to the Jewelers’ Security Alliance, the New York City–based industry crime-prevention group.

“They have been soaring for the last few years, and they are continuing to soar,” says JSA president John Kennedy, noting that they are among the hardest types of thefts to prevent. The crimes have occurred in 35 states, most frequently in Texas, California, and Florida. While the majority of losses fall between $5,000 and $20,000, others have reached $200,000.

Kennedy blames the recession for this recent spike: “They are one of the few kinds of crimes that would increase due to the poor economy, because these are not typically done by professional thieves. They are usually desperate people who have to do desperate things.”

In perhaps the most notorious recent grab-and-run case, Jonathan Wesley Wiseman, 27, made local headlines in June and July in connection with robberies at eight stores in Pennsylvania and Delaware. He was apprehended by local police and the FBI on June 7 in Maryland, and was later indicted on two counts of felony shoplifting and one count of robbery in Delaware; in Pennsylvania, he was charged with robbery, theft, and criminal mischief.

David Craig Jewelers in Newtown, Pa., was a victim of one of the robberies. The thief “was appropriately dressed for someone his age,” recalls store owner David Rotenberg. “He said he wanted to buy an engagement ring for his girlfriend. He was looking for a princess cut in the $5,000 range.”

In retrospect, Rotenberg says, two things should have raised red flags. First, the thief walked around the store before asking for help. And once he had a ring in hand, he asked for a second above his price range. (Rotenberg took out a piece in line with his budget.) After getting the second ring, the man ran out of the store and into a getaway car.

Rotenberg ran after the robber, which he knows is counter to JSA’s advice: “I grew up in a blue-collar area. It was just a conditioned response.” The jeweler spotted the car’s make, which he later gave to police along with a clear picture of the perpetrator from the store’s video camera. “People need to check their security procedures,” Rotenberg says. “We weren’t able to prevent ourselves from being robbed, but we luckily had information to aid in his capture.”