Police were unable to trace a suspect when she reported the matter so she created her own profile on social media app Whisper, and waited to see if the person on her daughter’s phone would post any new pictures.
When she saw a picture she believed was the offender she commented through the app: “Hot”.
The man then sent her his “Snapchat” ID so they could have more contact - which enabled the mum to get his name and give it to police.
Police arrested Preston man Rohan Sharma, 21, of Cottam Green, Cottam.
But Sharma denies inciting a child to engage in sexual activity - alleging photos of him were sent by someone else - and is on trial at Preston Crown Court.
Prosecuting, Bob Golinski said: “ The prosecution say that although the girl was in fact 10 she told him she was 11. But he wasn’t put off. He wanted to find out where she lived and where she went to school.
“ He wanted pictures from her. She sent him pictures clearly showing that she was a little girl and he sent her a bare-chested picture of himself.”
The user asked her to meet and made lewd suggestions.
A day later the mother found the conversation and alerted police.