She inched farther out of sight, pressing up against a window. Then she took the receiver off the hook, placed it on the counter, and did what Horev had urged: dialed 911. The police, she thought, would trace the call and respond without her having to utter a word.
Horev had one other thought, she later recalled: "If I didn't call the police, what if they ended up hurting us? What if this ended up being a hostage situation?"
After her clandestine dialing, Horev scurried to join Silow and frightened customers on the floor of the Montgomery Avenue restaurant.
One of the men, whose face was also covered, had pulled a shotgun from a plastic bag and demanded cellphones.
Another, this one brandishing a handgun, asked for the manager. When Silow identified himself as one, the gunman forced him behind the counter and demanded money.
The robbery, which occurred around 9 p.m., lasted just minutes with nobody injured, aside from some rattled nerves. Horev thinks the gunmen may have been scared away by the presence of a car outside.
Finding no one on the phone line, the Lower Merion police called the number back, and later Silow phoned them to report the robbery, which had ended just before the police arrived.
Lower Merion police said the robbers, possibly as many as four, got away with an undisclosed amount of cash. They carried handguns and a shotgun.
A day after the brazen and terrifying holdup at the restaurant that has been a mainstay on Montgomery Avenue since 1955, serving generations of families, life at Hymie's resumed Sunday amid a bustling brunch business.
Silow was back at work, as was Horev, who rang up orders at the register.
Customers - in person and by phone - expressed shock over the robbery and concern about those who had experienced it.
Owner Louis Barson's voicemail box was filled with messages. Due home Tuesday night from a family vacation in Montana, he instead boarded a 6 a.m. flight Sunday back to Philadelphia.
He arrived at Hymie's in the early afternoon, around the same time a Lower Merion police officer arrived to pick up surveillance video.
"It's extremely upsetting that this could possibly happen at 9 o'clock on a Saturday evening at my local neighborhood deli," said Barson, 45. "I would never have expected to get the phone call from my manager that we just had an armed robbery. My first question to him was, 'Is everybody OK?' and 'Thank God nobody was hurt.' "
Silow said customers took it personally, feeling "like somebody violated their space."
"If you live in this neighborhood, you're here three, four, five times a week," he said.
Your image might also be among those painted on the eatery's cream-colored walls.
Some customers have been frequenting Hymie's for breakfast, lunch, and dinner for more than four decades - as long as some staff members have worked there. When regulars don't show up as expected, the staff worries.
Customer Naomi Fenlin, 55, of Bryn Mawr, headed to the checkout counter Sunday with a basket filled with pounds of coleslaw, potato salad, and cheese - part of what she planned as Sunday dinner for at least 10. She was following in her parents' footsteps, she said.
"My family said this is where you have to go, and don't bring home anything else," Fenlin said.
In 1990, Barson, then a fresh-faced Temple University finance graduate, took over the family business. He grew up working in every corner of the deli, alongside longtime employees like Jerry Fox, known as "Silver Fox."
Barson's father, Sam, who bought the deli in the 1970s with partners, hired Fox 40 years ago. Now 81, Fox said he remembered telling the elder Barson he should hire him because he was a good man.
"I can give you an honest day's work," Fox remembered saying then.
The younger Barson had also grown up with many of his customers.
The running joke between Barson and general manager Harry Zeisler is when Barson asks Zeisler to take care of a customer because they're friends. Zeisler quickly retorts: "They're all your friends."
Horev wrapped up her shift Sunday afternoon and cashed out her register. In September, the resident of Merion Station will take on a new role: as a freshman at the University of Delaware, where she might major in communications, she said.
But on Sunday, people were calling her brave and a hero. At first, she didn't think of herself as either.
"I guess you could say I do see myself as brave enough to put my life on the line," she grudgingly allowed. "I did what I thought was best for everyone else."
Contact Darran Simon at 856-779-3829 or at firstname.lastname@example.org, or follow on Twitter @darransimon.