A person claims to know where stolen items are

One of the liars claims to know about thieves after they have stolen without anybody knowing, and he does that through means with which not many people are familiar. For example, he calls for a dish of water, and a child who has not yet reached puberty, who was breastfed by his mother for two full years, and who has never been scared by a dog. Then he starts to recite something from the Qur’aan, and some unintelligible words, then he asks the child, “Do you see anything in the water that is in the dish?” The child then describes the thief in detail and where he hid the stolen goods. What is the Islamic ruling on this? Is it permissible to pray behind this man and to keep in touch with him in good times and in bad – knowing that we have tried to advise him, but he did not accept the advice and he says that he is following the truth