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Army Lt. Jonathan David Rozier was 25 when he was killed by an unexploded rocket-propelled grenade in Baghdad on July 19, 2003. He left behind a wife and son who were suddenly faced with the harsh realities of being a single mother and growing up without a father present.

His wife Jessica Johns, who spoke with him just 12 hours before he was killed, had to quickly make some difficult decisions — one of which was what to do with Rozier's 1999 black Toyota Celica convertible.

Lieutenant Jonathan David Rozier holds his son, Justin. Courtesy Family

Their son Justin was only a few months old at the time and Johns was able to return the car to Toyota, forfeiting the loan to help pay for his daycare.

“I didn’t want to keep chipping away at my savings to pay for a car that nobody was using," she recalls. "It was just sitting in my driveway."

She returned the car and went on with the daily business of living, soon forgetting about it entirely.

Then this August, she came across the car registration while looking for a birth certificate. It triggered a flood of memories — and a bright idea.

Justin, now 15, had his permit and was planning to get his driver's license when he turned 16 next October. The car would be the ideal gift, and serve as a tribute to the father he missed.

“I wonder if this car is still out there? I was thinking I would go on a years-long search to find this car,” Jessica Johns, 36, told NBC News from Moore, Texas.

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Johns, a hunt coordinator for Santa Cruz Ranch, got a head start, posting her story on Facebook on Aug. 11, and asking those on social media for help. That would give her more than a year to track the car down in time for Justin's 16th birthday.

But that also included the challenge of keeping the search a secret from Justin — which translated to using every excuse possible to ban him from social media.

Fortunately, Johns heard back in just a few days.

The daughter of the car owner in Utah wrote Johns on Facebook, saying that her father might not want to sell it but giving her his phone number.

“If I call and he doesn’t want to sell it then my hopes would be crushed,” Johns said. “It took me 12 hours to get the courage to call him."

Lieutenant Jonathan David Rozier holds his son, Justin. Courtesy Family

When she did, Johns explained to the car's owner why his car meant so much to her. He said he needed to think about it first.

He called back an hour later.

“I think that your son will get more enjoyment out of having his dad’s car than I would,” she remembered him saying.

"I just got really excited,” she said.

But raising the funds to buy the car and refurbish it would be a challenge, so she again turned to social media.

Johns said a Utah-based organization called Follow The Flag got in touch. The group, which said its mission is to promote patriotism in America, helped with the fundraising effort and shipped the car to Justin in time for his 15th birthday.

“It’s what we do, it’s something we do in hopes of inspiring others,” said Kyle Fox, the founder of Follow The Flag. Fox said the entire project took about a month and a half to accomplish.

The big reveal took place at Justin's birthday party on a Saturday a few weeks ago.

“I started getting emotional because I never saw John drive that car home,” Johns said.

She said she remembers her son's expression when he looked up at the car and turned to her for confirmation.

"I was waiting for him, for it to click that’s dad’s car,” Johns said. “He starts looking at it, gets in, he looks so much like his dad."