It was one of the first nice days for a trip to the New Jersey Shore this summer, so Mary Henin and a friend piled into her car — a clunky but functioning 2008 Nissan — and headed for the beach.

Then, just as they arrived on Long Beach Island on May 29, they were surrounded by police, who surrounded the car, yelled at them to toss the keys out the window, and ordered them out of the car at gunpoint.

“I thought, ‘They must think I’m somebody else,‘” Henin recalled. “They tell me to put my hands up and back toward them, and then they immediately take my hands behind my back and handcuff me.” She remained in handcuffs, sitting by the side of the road, for about 45 minutes. That’s how long it took the Long Beach Township police to confirm the car was not stolen — but was, as Henin had been insisting, hers.

The source of the confusion? Henin’s car had been “courtesy towed” by Philadelphia police in February — removed from her West Philadelphia block because trees were being trimmed — and deposited at an unknown location with no record of its removal.

It’s a chaotic system that a January Inquirer investigation found often results in cars being effectively lost to their owners, left in illegal spots while parking tickets pile up like snowdrifts on the windshield.

» READ MORE: ‘What a nightmare’: How Philly police, parking authority, and tow companies lose cars while ‘courtesy’ towing

Owners are sometimes advised to report their cars stolen so police can look out for them. Henin followed that advice and filed the report. Then she spotted her car a few blocks from home and reported it found.

Henin, 31, a Philadelphia public defender, said she even made a follow-up phone call to make sure her car was no longer logged as stolen — and kept the “found” report in her glove box just in case of confusion — but she ended up in handcuffs anyway. She filed a citizen complaint, but two months later the investigation is still pending.

In her view, the situation is just one of many recent incidents that highlight the need for police oversight and accountability — for officers to recognize and rectify behavior that may seem minor but can have severe consequences.

“Something as simple as not filling out paperwork exposes Philadelphia citizens to the danger of police violence,” she said.

A Philadelphia police spokesperson, Staff Inspector Sekou Kinebrew, said he could not confirm whether the police, the Parking Authority or another entity had moved Henin’s car.

But, he said, “when she recovered the car and notified us, we should have taken it out of stolen status. ... That error is on us, and the investigation will determine that error was made and corrective action will be taken.”

No steps have been taken to revise policies around towing or tracking cars since the Inquirer investigation irevealed the scope of the problem, he said. However, he added the department is “always open to review and enhance” protocols as needed.

» READ MORE: Six Philly police were quietly fired, charged with abuse last year. Many will likely get their jobs back

Henin thinks the Long Beach Township police were unnecessarily aggressive, pointing guns, shouting and using handcuffs when Henin, who stands 4-foot-11, was being compliant — all over a car worth about $2,000 that was, implausibly, still being driven with the same plates three months after it was supposedly stolen.

“They introduced violence into a situation that did not warrant it,” she said. She recognizes that nothing they did violated what’s permitted. “One of the things I’ve really been reflecting on is permissible use of force is so much more dangerous than we acknowledge.”

Long Beach Township Police Chief Anthony Deely said his officers had conducted themselves according to protocol. That meant they had approached with necessary caution, but continued investigating the situation even after an initial call to Philadelphia police seemed to confirm Henin’s car was stolen and her arrest legitimate.

“This was a complete failure — not on our end — as far as timely information entered and removed which led to the confusion,” he said. “My sergeant on the scene received information from Philly PD, who said, ’Go ahead. Lock her up. It’s [a] good [arrest].‘ My sergeant went the extra yard because she had documentation.”

Henin made a complaint to the Philadelphia Police Department on June 1, and received a response from the Police Advisory Commission, a citizen oversight board that does not have authority over the department.

“There was also a hint of pessimism in my conversations [with the advisory commission], because there was this understanding that ... once this got into the hands of Internal Affairs, it would just be treated as a paperwork issue or even just a simple mistake,” she said.

The next week, Internal Affairs contacted her for an interview. Although the department has recognized an error occurred, Henin doesn’t expect much to come of the investigation. That’s why she thinks an independent oversight commission is needed: “The commission needs the strength to match the level of force police used against me and countless others who have suffered significantly worse harm.”