The picture of Yang Weixin that sparked the campaign

Hong Yuping's search for her son, abducted by human traffickers in 2009, sparked the current child beggar rescue campaign.

The 31-year-old from Fujian Province's Quanzhou City has tried everything to find seven-year-old Yang Weixin, even posing as a beggar herself at one point.

A picture of the boy was put online in January last year showing him on a street in Xiamen, also in Fujian, with one leg appearing to be broken, begging for coins.

"We left for Xiamen the day after we saw the picture," Hong's husband, Yang Bingjie, said.

Hong was pregnant at the time, but she stayed at a Xiamen railway station for 10 days and nights, waiting for her son to appear.

"We even entered a poor village where professional beggars lived but couldn't find out a clue," said Yang. Hong wore shabby clothing, picking up food from the street to avoid arousing suspicion.

In desperation, she wrote to Yu Jianrong, a professor at the Chinese Academy of Social Sciences, and Yu launched his campaign.

Hong wrote on the microblog to her son on Sunday: "Remember when we used to play hide and seek and your father pretended that he couldn't find you?

"You would shout out loud to give him hints. Now, baby, please give us some hints."