They call themselves Microchip Hunters.

According to its website, as quoted by the Evanston RoundTable, Microchip Hunters is a specialized volunteer team operating under the nonprofit Lost Dogs Illinois. Its members track down the owners of lost pets whose microchips are unregistered, outdated, or lead to a dead end.
In plain words: they are detectives for lost pets.
Jeanette Garlow, co-director of Lost Dogs Illinois, worked on Flor’s case. The team did their research, and they found what the old phone number could not tell them.
Flor’s family was living in Evanston.
Now someone had to get her there.
Garlow sent an email to Tanya Ohanian, the canine director at the Evanston Animal Shelter. She explained that there was a senior Chihuahua waiting in Griffith, Indiana, and asked whether someone might be able to pick her up and bring her home.
Ohanian was actually off work that week. She answered anyway.
Working remotely, she said yes immediately.
She posted the request on the shelter’s internal page for dog volunteers. And a volunteer named Gillian Primavera raised her hand. She offered to make the trip on Wednesday, right after her own work day ended.
Meanwhile, Ohanian made the phone call that Vanessa had been waiting twelve years to receive.
When Vanessa heard the news, Ohanian said, she immediately started crying.
Her Flor was alive.
That Wednesday evening, Primavera drove to Griffith, arriving around 8 p.m. The shelter volunteers there stayed open late, just so she could collect the little dog.
Then she turned the car around and headed straight for Evanston, with a very special passenger on board.
Waiting at the other end were Vanessa and four boys who were about to meet their big sister for the very first time.