(WIND NEWS) MT Zimny  was driving home from her in-laws' house with her husband, toddler and two golden retrievers when she received a text asking if they had their in-laws' 10-year-old dog, Finn.

Her in-laws, who live in Snohomish, Wash. — an hour away from Zimny and her family in Renton — had been searching the entire neighborhood for their black lab for half an hour. When they couldn’t find him, they finally thought to text.

"I asked my husband, 'Do we have Finn?' and he said, 'No, wait, why?' " Zimny tells PEOPLE, recalling how, at first glance, she only saw her daughter and the two golden retrievers.

But then, just to be safe, the family decided to pull over on the highway and check the back of the car just in case. Zimny unbuckled, crawled into the backseat and used the flashlight on her phone to look around. And sure enough, curled up under one of the golden retriever's legs, fast asleep, was Finn.

"I guess he saw us loading up the car," Zimny says. "He saw the golden retrievers hop into the back of the SUV, and he figured it was also his job to get in the car."

"It was so dark, and he's so dark, that no one noticed — except for my toddler," she adds. "As we were buckling her into her car seat, she kept saying, 'Bye-bye, Finn.' We realized later she was probably looking right at him, and we had no idea." Right away Zimny called her mother-in-law. When she answered the phone, Zimny, who's also an author, could tell she was super stressed. "I was like, 'Hey, we have your dog,' and she immediately burst out laughing," Zimny recall to PEOPLE.

"We were actually supposed to pet sit him this week anyway, so we figured we would just take him home early and he got two extra nights added to his vacation, and so did my in-laws because they left for their vacation early, too," she adds.

She continues, "He was like, let me just make this easier for everyone. Except then my in-laws had to drive his food down."

Zimny and her family eventually got home, and the next morning she decided to post about the incident on TikTok. After posting, she put her phone down and hung out with a friend for a few hours.

Later, she looked at her phone and the video had gone viral, amassing more than 6.6 million views and 9,500 comments.

"It was funny because so many people commented, 'How does this happen? This doesn't make sense to me,' " she adds. "But every chocolate lab owner would respond with, 'Yes, that tracks perfectly. This is chocolate lab behavior, especially when they’re that dark brown color. They blend in with everything.' "

"I also enjoyed seeing so many people joking, 'It’s a cousin sleepover!' " she adds. "Because, I mean, who among us, with cousins we like to hang out with, hasn’t tried to squeeze in an extra sleepover when we were growing up?"

With Finn going viral, Zimny hopes people take away a good laugh after they see the clip.

"I think, especially this time of year when it's so dark and gloomy, people are looking for a feel-good story. I had a lot of people saying, 'Oh, this was the best story I saw on the Internet today.' It makes me happy knowing that — even if they only watched my 30-second video about Finn — it cheered up some people's days."