What is the origin of the story of the penitent thief as a young boy?

During the Easter sermon our priest told a small story. It goes somewhat like this: > 'When Joseph, Mary and baby Jesus fled to Egypt, on the way there was a little boy who was given the task of searching (by Herod) the women for a small child(baby Jesus). And when he did see Him the boy smiled at Jesus and said "Remember me" and let them go. And years later when Christ was being crucified it was the same boy who was crucified on the right side of Christ. The little boy was the penitent thief who repented on the cross.' Now after this I came home and did a lot of searching on the net but nowhere did I come across such a story. My question is simple: Did these events actually happen or was this meant only as an inspiration for the gathering?