Specialist online investigator Greg Squire had hit a dead end in his efforts to rescue an abused girl his team had named Lucy.

Disturbing images of her were being shared on the dark web – an encrypted corner of the internet only accessible using special software designed to make owners digitally untraceable.

They contacted Facebook, which at the time dominated the social media landscape, asking for help scouring uploaded family photos – to see if Lucy was in any of them. But Facebook, despite having facial recognition technology, said it “did not have the tools” to help.

“So, I started just Googling bricks and it wasn’t too many searches [before] I found the Brick Industry Association,” says Squire.

“And the woman on the phone was awesome. She was like, ‘how can the brick industry help?'”

She offered to share the photo with brick experts all over the country. The response was almost immediate, he says.

The BBC asked Facebook why it couldn’t use its facial recognition technology to assist the hunt for Lucy. It responded: “To protect user privacy, it’s important that we follow the appropriate legal process, but we work to support law enforcement as much as we can.”